diff --git a/Dockerfile b/Dockerfile
index b064c4a..828f277 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -35,25 +35,37 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     procps \
     && rm -rf /var/lib/apt/lists/*
 
-# Build dump1090-fa from source (packages not available in slim repos)
+# Build dump1090-fa and acarsdec from source (packages not available in slim repos)
 RUN apt-get update && apt-get install -y --no-install-recommends \
     build-essential \
     git \
     pkg-config \
+    cmake \
     libncurses-dev \
+    libsndfile1-dev \
+    # Build dump1090
     && cd /tmp \
     && git clone --depth 1 https://github.com/flightaware/dump1090.git \
     && cd dump1090 \
     && make \
     && cp dump1090 /usr/bin/dump1090-fa \
     && ln -s /usr/bin/dump1090-fa /usr/bin/dump1090 \
-    && cd /app \
     && rm -rf /tmp/dump1090 \
+    # Build acarsdec
+    && cd /tmp \
+    && git clone --depth 1 https://github.com/TLeconte/acarsdec.git \
+    && cd acarsdec \
+    && mkdir build && cd build \
+    && cmake .. -Drtl=ON \
+    && make \
+    && cp acarsdec /usr/bin/acarsdec \
+    && rm -rf /tmp/acarsdec \
     # Cleanup build tools to reduce image size
     && apt-get remove -y \
         build-essential \
         git \
         pkg-config \
+        cmake \
         libncurses-dev \
     && apt-get autoremove -y \
     && rm -rf /var/lib/apt/lists/*
diff --git a/app.py b/app.py
index a5c06d7..efb3487 100644
--- a/app.py
+++ b/app.py
@@ -103,6 +103,11 @@ satellite_process = None
 satellite_queue = queue.Queue(maxsize=QUEUE_MAX_SIZE)
 satellite_lock = threading.Lock()
 
+# ACARS aircraft messaging
+acars_process = None
+acars_queue = queue.Queue(maxsize=QUEUE_MAX_SIZE)
+acars_lock = threading.Lock()
+
 # ============================================
 # GLOBAL STATE DICTIONARIES
 # ============================================
@@ -416,6 +421,7 @@ def health_check() -> Response:
             'pager': current_process is not None and (current_process.poll() is None if current_process else False),
             'sensor': sensor_process is not None and (sensor_process.poll() is None if sensor_process else False),
             'adsb': adsb_process is not None and (adsb_process.poll() is None if adsb_process else False),
+            'acars': acars_process is not None and (acars_process.poll() is None if acars_process else False),
             'wifi': wifi_process is not None and (wifi_process.poll() is None if wifi_process else False),
             'bluetooth': bt_process is not None and (bt_process.poll() is None if bt_process else False),
         },
@@ -431,7 +437,7 @@ def health_check() -> Response:
 @app.route('/killall', methods=['POST'])
 def kill_all() -> Response:
     """Kill all decoder and WiFi processes."""
-    global current_process, sensor_process, wifi_process, adsb_process
+    global current_process, sensor_process, wifi_process, adsb_process, acars_process
 
     # Import adsb module to reset its state
     from routes import adsb as adsb_module
@@ -440,7 +446,7 @@ def kill_all() -> Response:
     processes_to_kill = [
         'rtl_fm', 'multimon-ng', 'rtl_433',
         'airodump-ng', 'aireplay-ng', 'airmon-ng',
-        'dump1090'
+        'dump1090', 'acarsdec'
     ]
 
     for proc in processes_to_kill:
@@ -465,6 +471,10 @@ def kill_all() -> Response:
         adsb_process = None
         adsb_module.adsb_using_service = False
 
+    # Reset ACARS state
+    with acars_lock:
+        acars_process = None
+
     return jsonify({'status': 'killed', 'processes': killed})
 
 
@@ -517,7 +527,7 @@ def main() -> None:
 
     print("=" * 50)
     print("  INTERCEPT // Signal Intelligence")
-    print("  Pager / 433MHz / Aircraft / Satellite / WiFi / BT")
+    print("  Pager / 433MHz / Aircraft / ACARS / Satellite / WiFi / BT")
     print("=" * 50)
     print()
 
diff --git a/routes/__init__.py b/routes/__init__.py
index 5b6a326..62cdc79 100644
--- a/routes/__init__.py
+++ b/routes/__init__.py
@@ -7,6 +7,7 @@ def register_blueprints(app):
     from .wifi import wifi_bp
     from .bluetooth import bluetooth_bp
     from .adsb import adsb_bp
+    from .acars import acars_bp
     from .satellite import satellite_bp
     from .gps import gps_bp
     from .settings import settings_bp
@@ -18,6 +19,7 @@ def register_blueprints(app):
     app.register_blueprint(wifi_bp)
     app.register_blueprint(bluetooth_bp)
     app.register_blueprint(adsb_bp)
+    app.register_blueprint(acars_bp)
     app.register_blueprint(satellite_bp)
     app.register_blueprint(gps_bp)
     app.register_blueprint(settings_bp)
diff --git a/routes/acars.py b/routes/acars.py
new file mode 100644
index 0000000..c79ceff
--- /dev/null
+++ b/routes/acars.py
@@ -0,0 +1,290 @@
+"""ACARS aircraft messaging routes."""
+
+from __future__ import annotations
+
+import json
+import queue
+import shutil
+import subprocess
+import threading
+import time
+from datetime import datetime
+from typing import Generator
+
+from flask import Blueprint, jsonify, request, Response
+
+import app as app_module
+from utils.logging import sensor_logger as logger
+from utils.validation import validate_device_index, validate_gain, validate_ppm
+from utils.sse import format_sse
+from utils.constants import (
+    PROCESS_TERMINATE_TIMEOUT,
+    SSE_KEEPALIVE_INTERVAL,
+    SSE_QUEUE_TIMEOUT,
+    PROCESS_START_WAIT,
+)
+
+acars_bp = Blueprint('acars', __name__, url_prefix='/acars')
+
+# Default VHF ACARS frequencies (MHz) - common worldwide
+DEFAULT_ACARS_FREQUENCIES = [
+    '131.550',  # Primary worldwide
+    '130.025',  # Secondary USA/Canada
+    '129.125',  # USA
+    '131.525',  # Europe
+    '131.725',  # Europe secondary
+]
+
+# Message counter for statistics
+acars_message_count = 0
+acars_last_message_time = None
+
+
+def find_acarsdec():
+    """Find acarsdec binary."""
+    return shutil.which('acarsdec')
+
+
+def stream_acars_output(process: subprocess.Popen) -> None:
+    """Stream acarsdec JSON output to queue."""
+    global acars_message_count, acars_last_message_time
+
+    try:
+        app_module.acars_queue.put({'type': 'status', 'status': 'started'})
+
+        for line in iter(process.stdout.readline, b''):
+            line = line.decode('utf-8', errors='replace').strip()
+            if not line:
+                continue
+
+            try:
+                # acarsdec -j outputs JSON, one message per line
+                data = json.loads(line)
+
+                # Add our metadata
+                data['type'] = 'acars'
+                data['timestamp'] = datetime.utcnow().isoformat() + 'Z'
+
+                # Update stats
+                acars_message_count += 1
+                acars_last_message_time = time.time()
+
+                app_module.acars_queue.put(data)
+
+                # Log if enabled
+                if app_module.logging_enabled:
+                    try:
+                        with open(app_module.log_file_path, 'a') as f:
+                            ts = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
+                            f.write(f"{ts} | ACARS | {json.dumps(data)}\n")
+                    except Exception:
+                        pass
+
+            except json.JSONDecodeError:
+                # Not JSON - could be status message
+                if line:
+                    logger.debug(f"acarsdec non-JSON: {line[:100]}")
+
+    except Exception as e:
+        logger.error(f"ACARS stream error: {e}")
+        app_module.acars_queue.put({'type': 'error', 'message': str(e)})
+    finally:
+        app_module.acars_queue.put({'type': 'status', 'status': 'stopped'})
+        with app_module.acars_lock:
+            app_module.acars_process = None
+
+
+@acars_bp.route('/tools')
+def check_acars_tools() -> Response:
+    """Check for ACARS decoding tools."""
+    has_acarsdec = find_acarsdec() is not None
+
+    return jsonify({
+        'acarsdec': has_acarsdec,
+        'ready': has_acarsdec
+    })
+
+
+@acars_bp.route('/status')
+def acars_status() -> Response:
+    """Get ACARS decoder status."""
+    running = False
+    if app_module.acars_process:
+        running = app_module.acars_process.poll() is None
+
+    return jsonify({
+        'running': running,
+        'message_count': acars_message_count,
+        'last_message_time': acars_last_message_time,
+        'queue_size': app_module.acars_queue.qsize()
+    })
+
+
+@acars_bp.route('/start', methods=['POST'])
+def start_acars() -> Response:
+    """Start ACARS decoder."""
+    global acars_message_count, acars_last_message_time
+
+    with app_module.acars_lock:
+        if app_module.acars_process and app_module.acars_process.poll() is None:
+            return jsonify({
+                'status': 'error',
+                'message': 'ACARS decoder already running'
+            }), 409
+
+    # Check for acarsdec
+    acarsdec_path = find_acarsdec()
+    if not acarsdec_path:
+        return jsonify({
+            'status': 'error',
+            'message': 'acarsdec not found. Install with: sudo apt install acarsdec'
+        }), 400
+
+    data = request.json or {}
+
+    # Validate inputs
+    try:
+        device = validate_device_index(data.get('device', '0'))
+        gain = validate_gain(data.get('gain', '40'))
+        ppm = validate_ppm(data.get('ppm', '0'))
+    except ValueError as e:
+        return jsonify({'status': 'error', 'message': str(e)}), 400
+
+    # Get frequencies - use provided or defaults
+    frequencies = data.get('frequencies', DEFAULT_ACARS_FREQUENCIES)
+    if isinstance(frequencies, str):
+        frequencies = [f.strip() for f in frequencies.split(',')]
+
+    # Clear queue
+    while not app_module.acars_queue.empty():
+        try:
+            app_module.acars_queue.get_nowait()
+        except queue.Empty:
+            break
+
+    # Reset stats
+    acars_message_count = 0
+    acars_last_message_time = None
+
+    # Build acarsdec command
+    # acarsdec -j -r <device> -g <gain> -p <ppm> <freq1> <freq2> ...
+    cmd = [
+        acarsdec_path,
+        '-j',                    # JSON output
+        '-r', str(device),       # RTL-SDR device index
+    ]
+
+    # Add gain if not auto
+    if gain and str(gain) != '0':
+        cmd.extend(['-g', str(gain)])
+
+    # Add PPM correction if specified
+    if ppm and str(ppm) != '0':
+        cmd.extend(['-p', str(ppm)])
+
+    # Add frequencies
+    cmd.extend(frequencies)
+
+    logger.info(f"Starting ACARS decoder: {' '.join(cmd)}")
+
+    try:
+        process = subprocess.Popen(
+            cmd,
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE,
+            start_new_session=True
+        )
+
+        # Wait briefly to check if process started
+        time.sleep(PROCESS_START_WAIT)
+
+        if process.poll() is not None:
+            # Process died
+            stderr = ''
+            if process.stderr:
+                stderr = process.stderr.read().decode('utf-8', errors='replace')
+            error_msg = f'acarsdec failed to start'
+            if stderr:
+                error_msg += f': {stderr[:200]}'
+            logger.error(error_msg)
+            return jsonify({'status': 'error', 'message': error_msg}), 500
+
+        app_module.acars_process = process
+
+        # Start output streaming thread
+        thread = threading.Thread(
+            target=stream_acars_output,
+            args=(process,),
+            daemon=True
+        )
+        thread.start()
+
+        return jsonify({
+            'status': 'started',
+            'frequencies': frequencies,
+            'device': device,
+            'gain': gain
+        })
+
+    except Exception as e:
+        logger.error(f"Failed to start ACARS decoder: {e}")
+        return jsonify({'status': 'error', 'message': str(e)}), 500
+
+
+@acars_bp.route('/stop', methods=['POST'])
+def stop_acars() -> Response:
+    """Stop ACARS decoder."""
+    with app_module.acars_lock:
+        if not app_module.acars_process:
+            return jsonify({
+                'status': 'error',
+                'message': 'ACARS decoder not running'
+            }), 400
+
+        try:
+            app_module.acars_process.terminate()
+            app_module.acars_process.wait(timeout=PROCESS_TERMINATE_TIMEOUT)
+        except subprocess.TimeoutExpired:
+            app_module.acars_process.kill()
+        except Exception as e:
+            logger.error(f"Error stopping ACARS: {e}")
+
+        app_module.acars_process = None
+
+    return jsonify({'status': 'stopped'})
+
+
+@acars_bp.route('/stream')
+def stream_acars() -> Response:
+    """SSE stream for ACARS messages."""
+    def generate() -> Generator[str, None, None]:
+        last_keepalive = time.time()
+
+        while True:
+            try:
+                msg = app_module.acars_queue.get(timeout=SSE_QUEUE_TIMEOUT)
+                last_keepalive = time.time()
+                yield format_sse(msg)
+            except queue.Empty:
+                now = time.time()
+                if now - last_keepalive >= SSE_KEEPALIVE_INTERVAL:
+                    yield format_sse({'type': 'keepalive'})
+                    last_keepalive = now
+
+    response = Response(generate(), mimetype='text/event-stream')
+    response.headers['Cache-Control'] = 'no-cache'
+    response.headers['X-Accel-Buffering'] = 'no'
+    return response
+
+
+@acars_bp.route('/frequencies')
+def get_frequencies() -> Response:
+    """Get default ACARS frequencies."""
+    return jsonify({
+        'default': DEFAULT_ACARS_FREQUENCIES,
+        'regions': {
+            'north_america': ['129.125', '130.025', '130.450', '131.550'],
+            'europe': ['131.525', '131.725', '131.550'],
+            'asia_pacific': ['131.550', '131.450'],
+        }
+    })
diff --git a/setup.sh b/setup.sh
index f7d405f..66a0f65 100755
--- a/setup.sh
+++ b/setup.sh
@@ -139,6 +139,7 @@ check_tools() {
   check_required "multimon-ng" "Pager decoder" multimon-ng
   check_required "rtl_433"     "433MHz sensor decoder" rtl_433 rtl433
   check_required "dump1090"    "ADS-B decoder" dump1090
+  check_required "acarsdec"    "ACARS decoder" acarsdec
 
   echo
   info "GPS:"
@@ -305,7 +306,7 @@ install_multimon_ng_from_source_macos() {
 }
 
 install_macos_packages() {
-  TOTAL_STEPS=12
+  TOTAL_STEPS=13
   CURRENT_STEP=0
 
   progress "Checking Homebrew"
@@ -331,6 +332,9 @@ install_macos_packages() {
   progress "Installing dump1090"
   (brew_install dump1090-mutability) || warn "dump1090 not available via Homebrew"
 
+  progress "Installing acarsdec"
+  (brew_install acarsdec) || warn "acarsdec not available via Homebrew"
+
   progress "Installing aircrack-ng"
   brew_install aircrack-ng
 
@@ -412,6 +416,34 @@ install_dump1090_from_source_debian() {
   )
 }
 
+install_acarsdec_from_source_debian() {
+  info "acarsdec not available via APT. Building from source..."
+
+  apt_install build-essential git cmake \
+    librtlsdr-dev libusb-1.0-0-dev libsndfile1-dev
+
+  # Run in subshell to isolate EXIT trap
+  (
+    tmp_dir="$(mktemp -d)"
+    trap 'rm -rf "$tmp_dir"' EXIT
+
+    info "Cloning acarsdec..."
+    git clone --depth 1 https://github.com/TLeconte/acarsdec.git "$tmp_dir/acarsdec" >/dev/null 2>&1 \
+      || { warn "Failed to clone acarsdec"; exit 1; }
+
+    cd "$tmp_dir/acarsdec"
+    mkdir -p build && cd build
+
+    info "Compiling acarsdec..."
+    if cmake .. -Drtl=ON >/dev/null 2>&1 && make >/dev/null 2>&1; then
+      $SUDO install -m 0755 acarsdec /usr/local/bin/acarsdec
+      ok "acarsdec installed successfully."
+    else
+      warn "Failed to build acarsdec from source. ACARS decoding will not be available."
+    fi
+  )
+}
+
 setup_udev_rules_debian() {
   [[ -d /etc/udev/rules.d ]] || { warn "udev not found; skipping RTL-SDR udev rules."; return 0; }
 
@@ -464,7 +496,7 @@ install_debian_packages() {
   export DEBIAN_FRONTEND=noninteractive
   export NEEDRESTART_MODE=a
 
-  TOTAL_STEPS=16
+  TOTAL_STEPS=17
   CURRENT_STEP=0
 
   progress "Updating APT package lists"
@@ -520,6 +552,12 @@ install_debian_packages() {
   fi
   cmd_exists dump1090 || install_dump1090_from_source_debian
 
+  progress "Installing acarsdec"
+  if ! cmd_exists acarsdec; then
+    apt_install acarsdec || true
+  fi
+  cmd_exists acarsdec || install_acarsdec_from_source_debian
+
   progress "Configuring udev rules"
   setup_udev_rules_debian
 
diff --git a/static/css/adsb_dashboard.css b/static/css/adsb_dashboard.css
index 1af7360..72074de 100644
--- a/static/css/adsb_dashboard.css
+++ b/static/css/adsb_dashboard.css
@@ -185,13 +185,138 @@ body {
     position: relative;
     z-index: 10;
     display: grid;
-    grid-template-columns: 1fr 340px;
+    grid-template-columns: 1fr auto 300px;
     grid-template-rows: 1fr auto;
     gap: 0;
     height: calc(100vh - 60px);
     min-height: 500px;
 }
 
+/* ACARS sidebar (between map and main sidebar) - Collapsible */
+.acars-sidebar {
+    background: var(--bg-panel);
+    border-left: 1px solid var(--border-color);
+    display: flex;
+    flex-direction: row;
+    overflow: hidden;
+    transition: width 0.3s ease;
+    width: 280px;
+}
+
+.acars-sidebar.collapsed {
+    width: 32px;
+}
+
+.acars-collapse-btn {
+    width: 32px;
+    min-width: 32px;
+    background: var(--bg-card);
+    border: none;
+    border-right: 1px solid var(--border-color);
+    color: var(--accent-cyan);
+    cursor: pointer;
+    display: flex;
+    flex-direction: column;
+    align-items: center;
+    justify-content: center;
+    gap: 8px;
+    padding: 10px 0;
+    transition: background 0.2s;
+}
+
+.acars-collapse-btn:hover {
+    background: rgba(74, 158, 255, 0.1);
+}
+
+.acars-collapse-label {
+    writing-mode: vertical-rl;
+    text-orientation: mixed;
+    font-size: 10px;
+    font-weight: 600;
+    letter-spacing: 2px;
+    text-transform: uppercase;
+}
+
+.acars-sidebar.collapsed .acars-collapse-label {
+    display: block;
+}
+
+.acars-sidebar:not(.collapsed) .acars-collapse-label {
+    display: none;
+}
+
+#acarsCollapseIcon {
+    font-size: 10px;
+    transition: transform 0.3s;
+}
+
+.acars-sidebar.collapsed #acarsCollapseIcon {
+    transform: rotate(180deg);
+}
+
+.acars-sidebar-content {
+    flex: 1;
+    display: flex;
+    flex-direction: column;
+    overflow: hidden;
+    min-width: 0;
+}
+
+.acars-sidebar.collapsed .acars-sidebar-content {
+    display: none;
+}
+
+.acars-sidebar .panel {
+    flex: 1;
+    display: flex;
+    flex-direction: column;
+    border: none;
+    border-radius: 0;
+}
+
+.acars-sidebar .panel::before {
+    display: none;
+}
+
+.acars-sidebar .acars-messages {
+    flex: 1;
+    overflow-y: auto;
+    min-height: 0;
+}
+
+.acars-sidebar .acars-btn {
+    background: var(--bg-card);
+    border: 1px solid var(--accent-cyan);
+    color: var(--accent-cyan);
+    padding: 6px 10px;
+    font-size: 10px;
+    font-weight: 600;
+    cursor: pointer;
+    transition: all 0.2s;
+    text-transform: uppercase;
+    letter-spacing: 1px;
+}
+
+.acars-sidebar .acars-btn:hover {
+    background: rgba(74, 158, 255, 0.2);
+}
+
+.acars-message-item {
+    padding: 8px 10px;
+    border-bottom: 1px solid var(--border-color);
+    font-size: 10px;
+    animation: fadeIn 0.3s ease;
+}
+
+.acars-message-item:hover {
+    background: rgba(74, 158, 255, 0.05);
+}
+
+@keyframes fadeIn {
+    from { opacity: 0; transform: translateY(-5px); }
+    to { opacity: 1; transform: translateY(0); }
+}
+
 /* Panels */
 .panel {
     background: var(--bg-panel);
@@ -228,8 +353,14 @@ body {
 .panel-indicator {
     width: 6px;
     height: 6px;
-    background: var(--accent-cyan);
+    background: var(--text-dim);
     border-radius: 50%;
+    opacity: 0.5;
+}
+
+.panel-indicator.active {
+    background: var(--accent-green);
+    opacity: 1;
     animation: blink 1s ease-in-out infinite;
 }
 
@@ -656,8 +787,20 @@ body {
     opacity: 0.5;
 }
 
-/* Responsive */
-@media (max-width: 1000px) {
+/* Responsive - medium screens (hide ACARS sidebar, keep main sidebar) */
+@media (max-width: 1200px) {
+    .dashboard {
+        grid-template-columns: 1fr 300px;
+        grid-template-rows: 1fr auto;
+    }
+
+    .acars-sidebar {
+        display: none;
+    }
+}
+
+/* Responsive - small screens (single column) */
+@media (max-width: 900px) {
     .dashboard {
         grid-template-columns: 1fr;
         grid-template-rows: 1fr auto auto;
@@ -667,6 +810,10 @@ body {
         min-height: 400px;
     }
 
+    .acars-sidebar {
+        display: none;
+    }
+
     .sidebar {
         grid-column: 1;
         grid-row: 2;
diff --git a/templates/adsb_dashboard.html b/templates/adsb_dashboard.html
index c7de9fd..07fcb70 100644
--- a/templates/adsb_dashboard.html
+++ b/templates/adsb_dashboard.html
@@ -53,6 +53,52 @@
             </div>
         </div>
 
+        <!-- ACARS Panel (right of map) - Collapsible -->
+        <div class="acars-sidebar" id="acarsSidebar">
+            <button class="acars-collapse-btn" id="acarsCollapseBtn" onclick="toggleAcarsSidebar()" title="Toggle ACARS Panel">
+                <span id="acarsCollapseIcon">◀</span>
+                <span class="acars-collapse-label">ACARS</span>
+            </button>
+            <div class="acars-sidebar-content" id="acarsSidebarContent">
+                <div class="panel acars-panel">
+                    <div class="panel-header">
+                        <span>ACARS MESSAGES</span>
+                        <div style="display: flex; align-items: center; gap: 8px;">
+                            <span id="acarsCount" style="font-size: 10px; color: var(--accent-cyan);">0</span>
+                            <div class="panel-indicator" id="acarsPanelIndicator"></div>
+                        </div>
+                    </div>
+                    <div id="acarsPanelContent">
+                        <div class="acars-info" style="font-size: 9px; color: var(--text-muted); padding: 5px 8px; border-bottom: 1px solid var(--border-color);">
+                            <span style="color: var(--accent-yellow);">⚠</span> Requires separate SDR (VHF ~131 MHz)
+                        </div>
+                        <div class="acars-controls" style="padding: 8px; border-bottom: 1px solid var(--border-color);">
+                            <div style="display: flex; gap: 5px; margin-bottom: 5px;">
+                                <select id="acarsDeviceSelect" style="flex: 1; font-size: 10px;">
+                                    <option value="0">SDR 0</option>
+                                    <option value="1">SDR 1</option>
+                                </select>
+                                <select id="acarsRegionSelect" onchange="setAcarsFreqs()" style="flex: 1; font-size: 10px;">
+                                    <option value="na">N. America</option>
+                                    <option value="eu">Europe</option>
+                                    <option value="ap">Asia-Pac</option>
+                                </select>
+                            </div>
+                            <button class="acars-btn" id="acarsToggleBtn" onclick="toggleAcars()" style="width: 100%;">
+                                ▶ START ACARS
+                            </button>
+                        </div>
+                        <div class="acars-messages" id="acarsMessages">
+                            <div class="no-aircraft" style="padding: 20px; text-align: center;">
+                                <div style="font-size: 10px; color: var(--text-muted);">No ACARS messages</div>
+                                <div style="font-size: 9px; color: var(--text-dim); margin-top: 5px;">Start ACARS to receive aircraft datalink messages</div>
+                            </div>
+                        </div>
+                    </div>
+                </div>
+            </div>
+        </div>
+
         <!-- Sidebar -->
         <div class="sidebar">
             <!-- View Toggle -->
@@ -2215,6 +2261,179 @@ sudo make install</code>
         // Initialize airband on page load
         document.addEventListener('DOMContentLoaded', initAirband);
 
+        // ============================================
+        // ACARS Functions
+        // ============================================
+        let acarsEventSource = null;
+        let isAcarsRunning = false;
+        let acarsMessageCount = 0;
+        let acarsSidebarCollapsed = localStorage.getItem('acarsSidebarCollapsed') === 'true';
+        let acarsFrequencies = {
+            'na': ['129.125', '130.025', '130.450', '131.550'],
+            'eu': ['131.525', '131.725', '131.550'],
+            'ap': ['131.550', '131.450']
+        };
+
+        function toggleAcarsSidebar() {
+            const sidebar = document.getElementById('acarsSidebar');
+            acarsSidebarCollapsed = !acarsSidebarCollapsed;
+            sidebar.classList.toggle('collapsed', acarsSidebarCollapsed);
+            localStorage.setItem('acarsSidebarCollapsed', acarsSidebarCollapsed);
+        }
+
+        // Initialize ACARS sidebar state
+        document.addEventListener('DOMContentLoaded', () => {
+            const sidebar = document.getElementById('acarsSidebar');
+            if (sidebar && acarsSidebarCollapsed) {
+                sidebar.classList.add('collapsed');
+            }
+        });
+
+        function setAcarsFreqs() {
+            // Just updates the region selection - frequencies are sent on start
+        }
+
+        function getAcarsRegionFreqs() {
+            const region = document.getElementById('acarsRegionSelect').value;
+            return acarsFrequencies[region] || acarsFrequencies['na'];
+        }
+
+        function toggleAcars() {
+            if (isAcarsRunning) {
+                stopAcars();
+            } else {
+                startAcars();
+            }
+        }
+
+        function startAcars() {
+            const device = document.getElementById('acarsDeviceSelect').value;
+            const frequencies = getAcarsRegionFreqs();
+
+            // Warn if using same device as ADS-B
+            if (isTracking && device === '0') {
+                const useAnyway = confirm(
+                    'Warning: ADS-B tracking may be using SDR device 0.\n\n' +
+                    'ACARS uses VHF frequencies (129-131 MHz) while ADS-B uses 1090 MHz.\n' +
+                    'You need TWO separate SDR devices to receive both simultaneously.\n\n' +
+                    'Click OK to start ACARS on device ' + device + ' anyway.'
+                );
+                if (!useAnyway) return;
+            }
+
+            fetch('/acars/start', {
+                method: 'POST',
+                headers: { 'Content-Type': 'application/json' },
+                body: JSON.stringify({ device, frequencies, gain: '40' })
+            })
+            .then(r => r.json())
+            .then(data => {
+                if (data.status === 'started') {
+                    isAcarsRunning = true;
+                    acarsMessageCount = 0;
+                    document.getElementById('acarsToggleBtn').textContent = '■ STOP ACARS';
+                    document.getElementById('acarsToggleBtn').style.background = 'var(--accent-red)';
+                    document.getElementById('acarsPanelIndicator').classList.add('active');
+                    startAcarsStream();
+                } else {
+                    alert('ACARS Error: ' + data.message);
+                }
+            })
+            .catch(err => alert('ACARS Error: ' + err));
+        }
+
+        function stopAcars() {
+            fetch('/acars/stop', { method: 'POST' })
+                .then(r => r.json())
+                .then(() => {
+                    isAcarsRunning = false;
+                    document.getElementById('acarsToggleBtn').textContent = '▶ START ACARS';
+                    document.getElementById('acarsToggleBtn').style.background = '';
+                    document.getElementById('acarsPanelIndicator').classList.remove('active');
+                    if (acarsEventSource) {
+                        acarsEventSource.close();
+                        acarsEventSource = null;
+                    }
+                });
+        }
+
+        function startAcarsStream() {
+            if (acarsEventSource) acarsEventSource.close();
+            acarsEventSource = new EventSource('/acars/stream');
+
+            acarsEventSource.onmessage = function(e) {
+                const data = JSON.parse(e.data);
+                if (data.type === 'acars') {
+                    acarsMessageCount++;
+                    document.getElementById('acarsCount').textContent = acarsMessageCount;
+                    addAcarsMessage(data);
+                }
+            };
+
+            acarsEventSource.onerror = function() {
+                console.error('ACARS stream error');
+            };
+        }
+
+        function addAcarsMessage(data) {
+            const container = document.getElementById('acarsMessages');
+
+            // Remove "no messages" placeholder if present
+            const placeholder = container.querySelector('.no-aircraft');
+            if (placeholder) placeholder.remove();
+
+            const msg = document.createElement('div');
+            msg.className = 'acars-message-item';
+            msg.style.cssText = 'padding: 6px 8px; border-bottom: 1px solid var(--border-color); font-size: 10px;';
+
+            const flight = data.flight || 'UNKNOWN';
+            const reg = data.reg || '';
+            const label = data.label || '';
+            const text = data.text || data.msg || '';
+            const time = new Date().toLocaleTimeString();
+
+            msg.innerHTML = `
+                <div style="display: flex; justify-content: space-between; margin-bottom: 2px;">
+                    <span style="color: var(--accent-cyan); font-weight: bold;">${flight}</span>
+                    <span style="color: var(--text-muted);">${time}</span>
+                </div>
+                ${reg ? `<div style="color: var(--text-muted); font-size: 9px;">Reg: ${reg}</div>` : ''}
+                ${label ? `<div style="color: var(--accent-green);">Label: ${label}</div>` : ''}
+                ${text ? `<div style="color: var(--text-primary); margin-top: 3px; word-break: break-word;">${text}</div>` : ''}
+            `;
+
+            container.insertBefore(msg, container.firstChild);
+
+            // Keep max 50 messages
+            while (container.children.length > 50) {
+                container.removeChild(container.lastChild);
+            }
+        }
+
+        // Populate ACARS device selector
+        document.addEventListener('DOMContentLoaded', () => {
+            fetch('/devices')
+                .then(r => r.json())
+                .then(devices => {
+                    const select = document.getElementById('acarsDeviceSelect');
+                    select.innerHTML = '';
+                    if (devices.length === 0) {
+                        select.innerHTML = '<option value="0">No SDR detected</option>';
+                    } else {
+                        devices.forEach((d, i) => {
+                            const opt = document.createElement('option');
+                            opt.value = d.index || i;
+                            opt.textContent = `Device ${d.index || i}: ${d.name || d.type || 'SDR'}`;
+                            select.appendChild(opt);
+                        });
+                        // Default to device 1 if available (device 0 likely used for ADS-B)
+                        if (devices.length > 1) {
+                            select.value = '1';
+                        }
+                    }
+                });
+        });
+
         // ============================================
         // SQUAWK CODE REFERENCE
         // ============================================
diff --git a/templates/index.html b/templates/index.html
index bea5f34..b2d583e 100644
--- a/templates/index.html
+++ b/templates/index.html
@@ -857,6 +857,50 @@
                     <button class="stop-btn" id="stopAdsbBtn" onclick="stopAdsbScan()" style="display: none;">
                         Stop Tracking
                     </button>
+
+                    <!-- ACARS Sub-section -->
+                    <div class="section" style="margin-top: 15px; border-top: 1px solid var(--border-color); padding-top: 15px;">
+                        <h3 style="display: flex; align-items: center; justify-content: space-between; cursor: pointer;" onclick="toggleAcarsPanel()">
+                            <span>ACARS Messaging</span>
+                            <span id="acarsToggleIcon" style="font-size: 10px; color: var(--text-secondary);">&#9660;</span>
+                        </h3>
+                        <div id="acarsPanel">
+                            <div class="info-text" style="margin-bottom: 10px;">
+                                Decode aircraft digital messages (ACARS) on VHF frequencies.
+                            </div>
+                            <div style="background: rgba(255,193,7,0.1); border: 1px solid var(--accent-yellow); border-radius: 4px; padding: 8px; margin-bottom: 10px; font-size: 10px;">
+                                <strong style="color: var(--accent-yellow);">⚠ Two SDRs Required</strong><br>
+                                <span style="color: var(--text-secondary);">ADS-B uses 1090 MHz, ACARS uses VHF (~131 MHz). To receive both simultaneously, you need two separate RTL-SDR devices.</span>
+                            </div>
+                            <div class="form-group">
+                                <label>Frequencies (MHz)</label>
+                                <input type="text" id="acarsFrequencies" value="131.550,130.025,129.125,131.525" placeholder="131.550,130.025,...">
+                                <div class="info-text" style="margin-top: 4px;">Comma-separated VHF ACARS frequencies</div>
+                            </div>
+                            <div class="form-group">
+                                <label>Gain (dB, 0 = auto)</label>
+                                <input type="text" id="acarsGain" value="40" placeholder="40">
+                            </div>
+                            <div class="form-group">
+                                <label>PPM Correction</label>
+                                <input type="text" id="acarsPpm" value="0" placeholder="0">
+                            </div>
+                            <div class="preset-buttons" style="margin-bottom: 10px;">
+                                <button class="preset-btn" onclick="setAcarsRegion('na')">N. America</button>
+                                <button class="preset-btn" onclick="setAcarsRegion('eu')">Europe</button>
+                                <button class="preset-btn" onclick="setAcarsRegion('ap')">Asia-Pacific</button>
+                            </div>
+                            <div class="info-text" style="margin-top: 8px; display: grid; grid-template-columns: auto auto; gap: 4px 8px; align-items: center;" id="acarsToolStatus">
+                                <span>acarsdec:</span><span class="tool-status" id="acarsdecStatus">Checking...</span>
+                            </div>
+                            <button class="run-btn" id="startAcarsBtn" onclick="startAcars()" style="margin-top: 10px;">
+                                Start ACARS
+                            </button>
+                            <button class="stop-btn" id="stopAcarsBtn" onclick="stopAcars()" style="display: none; margin-top: 10px;">
+                                Stop ACARS
+                            </button>
+                        </div>
+                    </div>
                 </div>
 
                 <!-- SATELLITE MODE -->
@@ -1189,18 +1233,55 @@
 
                 <!-- Aircraft Visualizations - Leaflet Map -->
                 <div class="wifi-visuals" id="aircraftVisuals" style="display: none;">
-                    <!-- Map Panel -->
-                    <div class="wifi-visual-panel" style="grid-column: span 2;">
-                        <h5 style="color: var(--accent-cyan); text-shadow: 0 0 10px var(--accent-cyan);">ADS-B AIRCRAFT TRACKING</h5>
-                        <div class="aircraft-map-container">
-                            <div class="map-header">
-                                <span id="radarTime">--:--:--</span>
-                                <span id="radarStatus">TRACKING</span>
+                    <!-- Map Panel with ACARS sidebar -->
+                    <div class="wifi-visual-panel" style="grid-column: span 2; display: flex; gap: 0;">
+                        <!-- Map -->
+                        <div style="flex: 1; display: flex; flex-direction: column;">
+                            <h5 style="color: var(--accent-cyan); text-shadow: 0 0 10px var(--accent-cyan); padding: 0 10px;">ADS-B AIRCRAFT TRACKING</h5>
+                            <div class="aircraft-map-container" style="flex: 1;">
+                                <div class="map-header">
+                                    <span id="radarTime">--:--:--</span>
+                                    <span id="radarStatus">TRACKING</span>
+                                </div>
+                                <div id="aircraftMap"></div>
+                                <div class="map-footer">
+                                    <span>AIRCRAFT: <span id="aircraftCount">0</span></span>
+                                    <span>CENTER: <span id="mapCenter">--</span></span>
+                                </div>
                             </div>
-                            <div id="aircraftMap"></div>
-                            <div class="map-footer">
-                                <span>AIRCRAFT: <span id="aircraftCount">0</span></span>
-                                <span>CENTER: <span id="mapCenter">--</span></span>
+                        </div>
+                        <!-- ACARS Sidebar (Collapsible) -->
+                        <div class="main-acars-sidebar" id="mainAcarsSidebar">
+                            <button class="main-acars-collapse-btn" onclick="toggleMainAcarsSidebar()" title="Toggle ACARS">
+                                <span id="mainAcarsCollapseIcon">◀</span>
+                                <span class="main-acars-collapse-label">ACARS</span>
+                            </button>
+                            <div class="main-acars-content" id="mainAcarsContent">
+                                <div style="padding: 8px; border-bottom: 1px solid var(--border-color);">
+                                    <h5 style="color: var(--accent-green); margin-bottom: 8px; font-size: 11px;">ACARS MESSAGES</h5>
+                                    <div style="font-size: 9px; color: var(--text-muted); margin-bottom: 8px;">
+                                        <span style="color: var(--accent-yellow);">⚠</span> Requires separate SDR
+                                    </div>
+                                    <div style="display: flex; gap: 4px; margin-bottom: 5px;">
+                                        <select id="mainAcarsDevice" style="flex: 1; font-size: 9px; padding: 3px;">
+                                            <option value="0">SDR 0</option>
+                                            <option value="1">SDR 1</option>
+                                        </select>
+                                        <select id="mainAcarsRegion" style="flex: 1; font-size: 9px; padding: 3px;">
+                                            <option value="na">N.America</option>
+                                            <option value="eu">Europe</option>
+                                            <option value="ap">Asia-Pac</option>
+                                        </select>
+                                    </div>
+                                    <button id="mainAcarsToggleBtn" onclick="toggleMainAcars()" style="width: 100%; padding: 5px; font-size: 9px; background: var(--bg-dark); border: 1px solid var(--accent-cyan); color: var(--accent-cyan); cursor: pointer;">
+                                        ▶ START
+                                    </button>
+                                </div>
+                                <div class="main-acars-messages" id="mainAcarsMessages" style="flex: 1; overflow-y: auto; font-size: 10px;">
+                                    <div style="padding: 15px; text-align: center; color: var(--text-muted);">
+                                        No ACARS messages
+                                    </div>
+                                </div>
                             </div>
                         </div>
                     </div>
@@ -1516,6 +1597,78 @@
                         0%, 100% { opacity: 0.3; transform: scale(0.8); }
                         50% { opacity: 1; transform: scale(1); }
                     }
+
+                    /* Main ACARS Sidebar (Collapsible) */
+                    .main-acars-sidebar {
+                        width: 220px;
+                        background: var(--bg-panel);
+                        border-left: 1px solid var(--border-color);
+                        display: flex;
+                        flex-direction: row;
+                        transition: width 0.3s ease;
+                    }
+                    .main-acars-sidebar.collapsed {
+                        width: 28px;
+                    }
+                    .main-acars-collapse-btn {
+                        width: 28px;
+                        min-width: 28px;
+                        background: rgba(0,0,0,0.3);
+                        border: none;
+                        border-right: 1px solid var(--border-color);
+                        color: var(--accent-cyan);
+                        cursor: pointer;
+                        display: flex;
+                        flex-direction: column;
+                        align-items: center;
+                        justify-content: center;
+                        gap: 6px;
+                        padding: 8px 0;
+                    }
+                    .main-acars-collapse-btn:hover {
+                        background: rgba(74, 158, 255, 0.1);
+                    }
+                    .main-acars-collapse-label {
+                        writing-mode: vertical-rl;
+                        text-orientation: mixed;
+                        font-size: 9px;
+                        font-weight: 600;
+                        letter-spacing: 1px;
+                    }
+                    .main-acars-sidebar.collapsed .main-acars-collapse-label { display: block; }
+                    .main-acars-sidebar:not(.collapsed) .main-acars-collapse-label { display: none; }
+                    #mainAcarsCollapseIcon {
+                        font-size: 9px;
+                        transition: transform 0.3s;
+                    }
+                    .main-acars-sidebar.collapsed #mainAcarsCollapseIcon {
+                        transform: rotate(180deg);
+                    }
+                    .main-acars-content {
+                        flex: 1;
+                        display: flex;
+                        flex-direction: column;
+                        overflow: hidden;
+                        min-width: 0;
+                    }
+                    .main-acars-sidebar.collapsed .main-acars-content {
+                        display: none;
+                    }
+                    .main-acars-messages {
+                        max-height: 350px;
+                    }
+                    .main-acars-msg {
+                        padding: 6px 8px;
+                        border-bottom: 1px solid var(--border-color);
+                        animation: fadeInMsg 0.3s ease;
+                    }
+                    .main-acars-msg:hover {
+                        background: rgba(74, 158, 255, 0.05);
+                    }
+                    @keyframes fadeInMsg {
+                        from { opacity: 0; transform: translateY(-3px); }
+                        to { opacity: 1; transform: translateY(0); }
+                    }
                 </style>
 
                 <!-- Satellite Dashboard (Embedded) -->
@@ -2264,6 +2417,7 @@
                 initBtRadar();
             } else if (mode === 'aircraft') {
                 checkAdsbTools();
+                checkAcarsTools();
                 initAircraftRadar();
             } else if (mode === 'satellite') {
                 initPolarPlot();
@@ -7207,6 +7361,274 @@
                 });
         }
 
+        // ============================================
+        // ACARS Functions
+        // ============================================
+        let acarsEventSource = null;
+        let isAcarsRunning = false;
+        let acarsMessageCount = 0;
+
+        function toggleAcarsPanel() {
+            const panel = document.getElementById('acarsPanel');
+            const icon = document.getElementById('acarsToggleIcon');
+            if (panel.style.display === 'none') {
+                panel.style.display = 'block';
+                icon.innerHTML = '&#9660;';
+            } else {
+                panel.style.display = 'none';
+                icon.innerHTML = '&#9654;';
+            }
+        }
+
+        function setAcarsRegion(region) {
+            const freqInput = document.getElementById('acarsFrequencies');
+            const regions = {
+                'na': '129.125,130.025,130.450,131.550',
+                'eu': '131.525,131.725,131.550',
+                'ap': '131.550,131.450'
+            };
+            freqInput.value = regions[region] || regions['na'];
+        }
+
+        function checkAcarsTools() {
+            fetch('/acars/tools')
+                .then(r => r.json())
+                .then(data => {
+                    const status = document.getElementById('acarsdecStatus');
+                    if (data.acarsdec) {
+                        status.textContent = 'OK';
+                        status.className = 'tool-status ok';
+                    } else {
+                        status.textContent = 'Missing';
+                        status.className = 'tool-status missing';
+                    }
+                })
+                .catch(() => {
+                    const status = document.getElementById('acarsdecStatus');
+                    status.textContent = 'Error';
+                    status.className = 'tool-status missing';
+                });
+        }
+
+        function startAcars() {
+            const frequencies = document.getElementById('acarsFrequencies').value.split(',').map(f => f.trim());
+            const gain = document.getElementById('acarsGain').value;
+            const ppm = document.getElementById('acarsPpm').value;
+            const device = getSelectedDevice();
+
+            fetch('/acars/start', {
+                method: 'POST',
+                headers: { 'Content-Type': 'application/json' },
+                body: JSON.stringify({ frequencies, gain, ppm, device })
+            })
+            .then(r => r.json())
+            .then(data => {
+                if (data.status === 'started') {
+                    isAcarsRunning = true;
+                    acarsMessageCount = 0;
+                    document.getElementById('startAcarsBtn').style.display = 'none';
+                    document.getElementById('stopAcarsBtn').style.display = 'block';
+                    startAcarsStream();
+                } else {
+                    alert('ACARS Error: ' + data.message);
+                }
+            })
+            .catch(err => alert('ACARS Error: ' + err));
+        }
+
+        function stopAcars() {
+            fetch('/acars/stop', { method: 'POST' })
+                .then(r => r.json())
+                .then(data => {
+                    isAcarsRunning = false;
+                    document.getElementById('startAcarsBtn').style.display = 'block';
+                    document.getElementById('stopAcarsBtn').style.display = 'none';
+                    if (acarsEventSource) {
+                        acarsEventSource.close();
+                        acarsEventSource = null;
+                    }
+                });
+        }
+
+        function startAcarsStream() {
+            if (acarsEventSource) acarsEventSource.close();
+            acarsEventSource = new EventSource('/acars/stream');
+
+            acarsEventSource.onmessage = function(e) {
+                const data = JSON.parse(e.data);
+                if (data.type === 'acars') {
+                    acarsMessageCount++;
+                    addAcarsToOutput(data);
+                } else if (data.type === 'error') {
+                    console.error('ACARS error:', data.message);
+                }
+            };
+
+            acarsEventSource.onerror = function() {
+                console.error('ACARS stream error');
+            };
+        }
+
+        function addAcarsToOutput(data) {
+            const output = document.getElementById('outputList');
+            const item = document.createElement('div');
+            item.className = 'output-item acars-message';
+
+            const flight = data.flight || 'Unknown';
+            const reg = data.reg || '';
+            const label = data.label || '';
+            const text = data.text || data.msg || '';
+
+            item.innerHTML = `
+                <span class="timestamp">${new Date().toLocaleTimeString()}</span>
+                <span class="acars-flight" style="color: var(--accent-cyan); font-weight: bold;">${flight}</span>
+                ${reg ? `<span class="acars-reg" style="color: var(--text-secondary);">[${reg}]</span>` : ''}
+                <span class="acars-label" style="color: var(--accent-green);">${label}</span>
+                <span class="acars-text">${text}</span>
+            `;
+
+            output.insertBefore(item, output.firstChild);
+
+            // Keep output manageable
+            while (output.children.length > 200) {
+                output.removeChild(output.lastChild);
+            }
+        }
+
+        // ============================================
+        // Main ACARS Sidebar (Collapsible - Aircraft Tab)
+        // ============================================
+        let mainAcarsSidebarCollapsed = localStorage.getItem('mainAcarsSidebarCollapsed') === 'true';
+        let mainAcarsEventSource = null;
+        let isMainAcarsRunning = false;
+        let mainAcarsMessageCount = 0;
+
+        // Initialize sidebar state on load
+        document.addEventListener('DOMContentLoaded', function() {
+            const sidebar = document.getElementById('mainAcarsSidebar');
+            if (sidebar && mainAcarsSidebarCollapsed) {
+                sidebar.classList.add('collapsed');
+            }
+        });
+
+        function toggleMainAcarsSidebar() {
+            const sidebar = document.getElementById('mainAcarsSidebar');
+            mainAcarsSidebarCollapsed = !mainAcarsSidebarCollapsed;
+            sidebar.classList.toggle('collapsed', mainAcarsSidebarCollapsed);
+            localStorage.setItem('mainAcarsSidebarCollapsed', mainAcarsSidebarCollapsed);
+        }
+
+        function toggleMainAcars() {
+            if (isMainAcarsRunning) {
+                stopMainAcars();
+            } else {
+                startMainAcars();
+            }
+        }
+
+        function startMainAcars() {
+            const device = document.getElementById('mainAcarsDevice').value;
+            const region = document.getElementById('mainAcarsRegion').value;
+
+            const regions = {
+                'na': ['129.125', '130.025', '130.450', '131.550'],
+                'eu': ['131.525', '131.725', '131.550'],
+                'ap': ['131.550', '131.450']
+            };
+            const frequencies = regions[region] || regions['na'];
+
+            fetch('/acars/start', {
+                method: 'POST',
+                headers: { 'Content-Type': 'application/json' },
+                body: JSON.stringify({ frequencies, device: parseInt(device), gain: 40 })
+            })
+            .then(r => r.json())
+            .then(data => {
+                if (data.status === 'started') {
+                    isMainAcarsRunning = true;
+                    mainAcarsMessageCount = 0;
+                    document.getElementById('mainAcarsToggleBtn').innerHTML = '■ STOP';
+                    document.getElementById('mainAcarsToggleBtn').style.background = 'var(--accent-red)';
+                    document.getElementById('mainAcarsToggleBtn').style.borderColor = 'var(--accent-red)';
+                    document.getElementById('mainAcarsToggleBtn').style.color = '#fff';
+                    startMainAcarsStream();
+                } else {
+                    alert('ACARS Error: ' + data.message);
+                }
+            })
+            .catch(err => alert('ACARS Error: ' + err));
+        }
+
+        function stopMainAcars() {
+            fetch('/acars/stop', { method: 'POST' })
+                .then(r => r.json())
+                .then(data => {
+                    isMainAcarsRunning = false;
+                    document.getElementById('mainAcarsToggleBtn').innerHTML = '▶ START';
+                    document.getElementById('mainAcarsToggleBtn').style.background = 'var(--bg-dark)';
+                    document.getElementById('mainAcarsToggleBtn').style.borderColor = 'var(--accent-cyan)';
+                    document.getElementById('mainAcarsToggleBtn').style.color = 'var(--accent-cyan)';
+                    if (mainAcarsEventSource) {
+                        mainAcarsEventSource.close();
+                        mainAcarsEventSource = null;
+                    }
+                });
+        }
+
+        function startMainAcarsStream() {
+            if (mainAcarsEventSource) mainAcarsEventSource.close();
+            mainAcarsEventSource = new EventSource('/acars/stream');
+
+            mainAcarsEventSource.onmessage = function(e) {
+                const data = JSON.parse(e.data);
+                if (data.type === 'acars') {
+                    mainAcarsMessageCount++;
+                    addMainAcarsMessage(data);
+                    // Also add to main output if ADS-B mode is active
+                    addAcarsToOutput(data);
+                }
+            };
+
+            mainAcarsEventSource.onerror = function() {
+                console.error('Main ACARS stream error');
+            };
+        }
+
+        function addMainAcarsMessage(data) {
+            const container = document.getElementById('mainAcarsMessages');
+
+            // Remove placeholder if present
+            const placeholder = container.querySelector('div[style*="text-align: center"]');
+            if (placeholder && placeholder.textContent.includes('No ACARS')) {
+                placeholder.remove();
+            }
+
+            const flight = data.flight || 'Unknown';
+            const reg = data.reg || '';
+            const text = data.text || data.msg || '';
+            const label = data.label || '';
+            const time = new Date().toLocaleTimeString('en-US', { hour12: false, hour: '2-digit', minute: '2-digit', second: '2-digit' });
+
+            const msgEl = document.createElement('div');
+            msgEl.className = 'main-acars-msg';
+            msgEl.innerHTML = `
+                <div style="display: flex; justify-content: space-between; align-items: center; margin-bottom: 2px;">
+                    <span style="color: var(--accent-cyan); font-weight: bold;">${flight}</span>
+                    <span style="color: var(--text-muted); font-size: 8px;">${time}</span>
+                </div>
+                ${reg ? `<div style="color: var(--text-secondary); font-size: 9px;">${reg}</div>` : ''}
+                ${label ? `<div style="color: var(--accent-green); font-size: 9px;">[${label}]</div>` : ''}
+                ${text ? `<div style="color: var(--text-primary); font-size: 9px; margin-top: 2px; word-break: break-word;">${text.substring(0, 100)}${text.length > 100 ? '...' : ''}</div>` : ''}
+            `;
+
+            container.insertBefore(msgEl, container.firstChild);
+
+            // Keep list manageable
+            while (container.children.length > 50) {
+                container.removeChild(container.lastChild);
+            }
+        }
+
         // Batching state for aircraft updates to prevent browser freeze
         let pendingAircraftUpdate = false;
         let pendingAircraftData = [];
diff --git a/utils/dependencies.py b/utils/dependencies.py
index aaac838..adf7e56 100644
--- a/utils/dependencies.py
+++ b/utils/dependencies.py
@@ -195,6 +195,20 @@ TOOL_DEPENDENCIES = {
             }
         }
     },
+    'acars': {
+        'name': 'Aircraft Messaging (ACARS)',
+        'tools': {
+            'acarsdec': {
+                'required': True,
+                'description': 'ACARS VHF decoder',
+                'install': {
+                    'apt': 'sudo apt install acarsdec',
+                    'brew': 'brew install acarsdec',
+                    'manual': 'https://github.com/TLeconte/acarsdec'
+                }
+            }
+        }
+    },
     'satellite': {
         'name': 'Satellite Tracking',
         'tools': {