WASHINGTON– Two Inertial Reference Units (IRUs) failed on a United Airlines (UA) Boeing 787-8 shortly before the aircraft experienced a rapid altitude shift over Africa on 24 January 2025, injuring 16 people. On March 18, the National Transportation Safety Board (NTSB) revealed the actual findings in a preliminary accident report.
According to the report, the jet’s left IRU failed approximately 1 hour and 5 minutes before the altitude upset. This was followed by the failure of the right IRU about 55 minutes later. The incident occurred at 01:31 Lagos time on January 24 during United flight 613 from Lagos (LOS) to Washington Dulles International Airport (IAD) while flying over Côte d’Ivoire (CI).
Photo: Clément AlloingUnited Airlines 787 IRUs Failure
United Airlines Flight 613 took off from Murtala Muhammed International Airport in Lagos (LOS) just before midnight, on January 23, 2025.
Approximately 93 minutes into the flight, the aircraft experienced a sudden descent. This caused baggage, personal items, food trays, and other objects to be violently tossed throughout the cabin, as documented in videos shared on social media platforms.
The Federal Airports Authority of Nigeria (FAAN) reported that the flight carried 243 passengers and 11 crew members. The aircraft safely returned to Lagos (LOS) and landed at approximately 3:22 a.m. on 24th January 2025.
Four passengers and two crew members required hospitalization for serious injuries but were subsequently discharged. An additional 27 passengers and five crew members reported suffering minor injuries.
United Airlines stated that the aircraft returned to Lagos due to a “technical issue.” The airline clarified that turbulence was not responsible for the sudden descent and indicated they are collaborating with aviation authorities in both the United States and Nigeria to determine the actual cause of the incident.
Only with the NTSB’s recent report release has it become clear that Inertial Reference Unit (IRU) failures were behind what United Airlines had previously described only as a “technical issue.”
United Airlines Flight #UA613 Makes Emergency Landing in Lagos: Six Seriously Injured Amid Mid-Air Incident
A United Airlines Boeing 787-8(N27903) Dreamliner, operating as flight UA613 from Lagos to Washington Dulles, was forced to return to Lagos after a mid-air technical issue… pic.twitter.com/FrHCjOpbN9
— Turbine Traveller (@Turbinetraveler) January 24, 2025
NTSB Report
The United flight UA613, operated with Boeing 787-8, registered as N27903, departed Lagos at approximately 00:20 and climbed to 36,000 feet. Following the IRU failures, and just seconds before the altitude upset, the autopilot automatically disconnected as cockpit master caution and master warning alerts activated. The pilots immediately took manual control of the aircraft.
The sudden altitude changes continued for approximately 12 minutes. During this period, the 787-8 deviated from its cruising altitude of 36,000 feet. It reached a maximum height of 36,203 feet and dropped to a minimum of 35,577 feet.
The NTSB report notes that the aircraft’s stick shaker was activated. Its auto-throttle was disconnected and then re-engaged before disconnecting a second time.
Boeing-787-8-Dreamliner;Photo: Wikimedia Commons by Toshi Aoki – JP SpottersInjuries and Response
The altitude excursions occurred during meal service in the cabin, contributing to the injuries. Of the 254 people aboard the jet, which included 11 crew members and 243 passengers, 15 passengers suffered minor injuries and one sustained serious injuries.
At 00:40, the flight crew decided to return to Lagos, where they landed safely.
Investigation Status
The location of the incident places primary investigative responsibility on Côte d’Ivoire authorities. Although they granted a request from the NTSB to assist with the investigation.
The 787-8 flight data recorders, inertial reference units, and attitude heading reference units were removed from the aircraft in Lagos and shipped to Washington, DC for examination.
The NTSB noted it was unable to access cockpit audio recordings during the event because the jet’s cockpit voice recorder only captures 2 hours of audio and had been overwritten by the time investigators could access it.
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