Event Overview
On January 24, 2025, about 00:31 UTC, United Airlines Flight 613, a Boeing 787-8, experienced altitude excursions while in cruise flight over Côte d'Ivoire airspace at 36,000 feet. The flight was operating under Part 121 as a scheduled international passenger service from Murtala Muhammed International Airport (LOS), Lagos, Nigeria, to Washington Dulles International Airport (IAD), Dulles, Virginia. On board were 11 crew members and 243 passengers.
Sequence of Events
Approximately 1 hour and 5 minutes before the event, inflight data indicated a left inertial reference unit (IRU) failure. About 55 minutes later, data indicated a right IRU failure. At 00:30:57, according to flight data recorder data, the autopilot disconnected automatically, and the flight crew took manual control. Master caution and master warning were recorded at that time. Altitude excursions began simultaneously. Three seconds later, the autothrottle disconnected. At 00:31:14, a stick shaker activation was recorded. Twenty seconds later, the autopilot was reengaged for one second, then disconnected automatically again. At 00:40:30, the airplane began a right turn back toward Lagos. At 00:44:39, the autopilot was reengaged and remained engaged until final approach into LOS.
The altitude excursions from 36,000 feet mean sea level lasted about 12 minutes, reaching a maximum altitude of 36,203 feet and a minimum of 35,577 feet. During this period, meal service was being conducted in the cabin, and injuries resulted.
Injuries and Response
One person sustained a serious injury and 15 people sustained minor injuries. The aircraft sustained minor damage. The flight crew elected to perform an air turn back and returned to LOS, where the airplane landed uneventfully. Emergency responders met the airplane upon landing and transported injured persons to a nearby clinic.
Investigation
Pursuant to ICAO Annex 13, the state of occurrence (Côte d'Ivoire) holds responsibility for the investigation and delegated it to the NTSB on January 27, 2025. The flight recorders, IRUs, and attitude heading reference units (AHRUs) were removed from the aircraft in Lagos and flown to IAD on February 3, 2025. The NTSB took possession of these components at IAD and transported them to NTSB headquarters for readout and testing. The flight data recorder was successfully downloaded; the cockpit voice recorder (with 2-hour recording capability) was read out and found to have the accident event overwritten.
NTSB specialists assigned include Operations and Human Performance, Airplane Systems, Survival Factors, and Flight Data Recorder. Parties to the investigation are the FAA, United Airlines, Boeing, Honeywell, and the Air Line Pilots Association (ALPA). The BEA Côte d'Ivoire provided an accredited representative. The investigation is ongoing.