Accident Summary
On March 13, 2025, at about 1759 mountain daylight time, American Airlines flight 1006, a Boeing 737-823 (registration N885NN), experienced engine vibrations during takeoff from Colorado Springs Airport (COS) in Colorado Springs, Colorado. The flight crew continued the takeoff, then diverted to and landed at Denver International Airport (DEN) in Denver, Colorado. After landing, the flight crew taxied to their assigned gate and shut down both engines. Shortly after shutdown, a fire broke out in the area of the No. 2 (right) engine, prompting an evacuation of the passengers and crew.
Flight Crew Actions
The first officer was the pilot flying, and the captain was the pilot monitoring. During takeoff, just before V1, the crew observed an exhaust gas temperature (EGT) over-temp indication for the No. 2 engine. After gear and flaps were retracted, power was slightly reduced on the No. 2 engine, and the EGT returned to within limits. During climbout, the captain noted high engine vibration indications for the right engine. The captain called for the High Engine Vibration checklist, and the first officer continued flying. The crew coordinated with American Airlines dispatch and determined Denver was the most reasonable diversion airport. The aircraft climbed to 16,000 feet mean sea level, the highest altitude reached during the flight. The approach and landing were normal; taxi to the gate took about five minutes.
Evacuation
After arriving at the gate, flight attendants heard passengers yelling “fire” and “smoke” and observed smoke filling the cabin. Attempts to contact the flight crew by interphone and by knocking on the cockpit door were made. Passengers began moving toward the exits. The flight attendants initiated an evacuation. Passengers used the L1 door (deplaning via the jetway bridge), both left overwing window exits, and the R2 door. The R2 evacuation slide deployed automatically. The L2 door was observed cracked open; maintenance later found the escape slide jammed in the door, preventing its operation. Left overwing evacuees left the wing using ground vehicles, ladders available in the gate area, and a belt loader. Post-event examination found the flaps remained at zero.
Post-Accident Findings
The fire was extinguished within one minute by gate ramp personnel before the arrival of Denver airport fire fighting and rescue (ARFF). Of the three ARFF trucks, one positioned on the right side sprayed water on the right aft fuselage and right inboard wing “hot spots” as indicated by infrared heat sensors. Video from Denver airport operations showed a trail of fluid leaking from under the right engine nacelle as the airplane taxied to the gate. Twelve passengers sustained minor injuries; the airplane received substantial damage. Visual meteorological conditions prevailed.
The airplane exhibited heat, smoke, and burn indications near the right engine nacelle, right wing, right side of the fuselage aft of the wing, the right main landing gear, and the right main landing gear wheel well. The right engine nacelle was intact but showed dark streaking consistent with in-flight streamlines, and the aft and bottom were sooted and thermally distressed, consistent with a ground fire.
Investigation
The airplane was towed to a local maintenance hangar for examination. It was powered by two CFM56-7B turbofan engines. Inspection of the right engine revealed all fan blades present, but one fan blade platform was fractured. The lockwire of a fuel fitting on the variable stator vane (VSV) was loose and installed in the incorrect direction. The VSV actuator rod end was incorrectly fastened and secured to the VSV actuator, allowing fuel to leak from the fitting. The VSV rod end muscle line was fractured in the weld, and the 6 o’clock seal drain line of the inboard thrust reverser half was blocked with sealant above the lower bifurcation fire seal and in the exit tube.
The L2 slide was found removed from its bustle and on the floor of the L2 passageway with its safety pin installed. The slide pack’s bannis latch moved freely; there were dark scuffs on the outboard side and a tear on the underside of the girt fabric.
The National Transportation Safety Board (NTSB) launched an investigation, forming operations, powerplants, airworthiness, and survival factors groups. The cockpit voice recorder (CVR) and flight data recorder (FDR) were sent to the NTSB headquarters for download and analysis. The CVR captured intelligible audio beginning while the aircraft was climbing from 15,000 to 16,000 feet and the crew performed the Engine High Vibration checklist. The cockpit area microphone channel recorded an hour of audio prior, but it was unintelligible. The FDR was in good condition, containing approximately 54 hours of data with over 1,000 parameters; the accident flight was the last recording, lasting about one hour.
Maintenance records for the right engine were reviewed. The damaged fan blade platform, rod end manifold, and aft exhaust plug were retained for further examination. The L2 slide was shipped to the manufacturer for detailed inspection, and its maintenance log will be reviewed.
Parties to the investigation include American Airlines, GE Aerospace, the Federal Aviation Administration (FAA), The Boeing Company, Allied Pilots Association, Transport Workers Union - International Association of Machinists and Aerospace Workers (TWU-IAM), Association of Professional Flight Attendants, and Denver Airport. In accordance with Annex 13 to the Convention on International Civil Aviation, the Bureau d’Enquetes et d’Analyses pour la securite de l’aviation civile (BEA) of France appointed an Accredited Representative, as the CFM International engine is a joint venture between GE Aerospace and Safran Aircraft Engines. Safran Aircraft Engines and the European Union Aviation Safety Agency (EASA) are technical advisors to BEA.
The investigation continues.