A 
United Airlines Boeing 777 was forced to return to 
San Francisco International Airport (SFO) on Tuesday after its crew shut down one of the aircraft’s engines during climb. Aerocorner reported that the nearly 29-year-old widebody was operating a scheduled service to Beijing when the problem occurred, prompting an unscheduled return about 90 minutes after departure.
The incident is the latest in a series of engine-related problems involving United’s 777-200 fleet, including a remarkably similar occurrence at SFO just three months earlier. With many first-generation 777s approaching three decades of service, United and other major airlines face increasingly important decisions about how long to retain these aircraft and when to replace them with newer widebodies.
United Boeing 777-200 Suffers Engine Shutdown After Departing San Francisco
Credit: Markus Mainka | Shutterstock
The Boeing 777-200ER, registered N796UA, according to Planespotters.net, was operating UA888 from San Francisco to 
Beijing Capital Airport (PEK) on October 6 when its right-hand Pratt & Whitney PW4090 engine reportedly began making loud noises and experiencing severe vibrations. According to The Aviation Herald, the crew stopped climbing at about 28,000 feet, shut down the affected engine, and returned to San Francisco, landing safely on Runway 28R about 90 minutes after departure. The aircraft has remained grounded since, and the cause of the malfunction has not yet been publicly established.
United delivered the aircraft new in January 1998, making it nearly 29 years old at the time of the incident. It is equipped with two PW4090 engines from Pratt & Whitney’s PW4000-112 family, which powered many early Boeing 777s. United has operated the type since 1995, and its oldest examples now rank among the longest-serving 777s still flying commercially. N796UA has spent its entire operating life with the airline, except for periods of storage, including during the pandemic.
Remarkably, N796UA also experienced a serious engine malfunction shortly after entering service. On July 29, 1998, the aircraft was departing 
London Heathrow Airport (LHR) for San Francisco when smoke entered its flight deck and cabin, followed by a loud bang and a complete loss of oil pressure in its left engine. The pilots shut down the engine and returned safely to Heathrow. The UK’s Air Accidents Investigation Branch found that a failed carbon seal caused rapid oil loss and internal engine damage.
“As a result of the seal’s failure, the engine oil contents were rapidly reduced from 17 US quarts to 0, leading to further damage and heating within the ‘No. 1 to 2’ compartment and the subsequent heating damage within the nacelle, exterior to the engine.”
United Has Experienced Several Boeing 777-200 Engine Failures
Credit: Wirestock Creators | Shutterstock
This week’s incident closely resembles an event earlier this year on July 9, when another 777-200ER, registered N228UA, was operating flight 926 from San Francisco to 
Frankfurt Airport (FRA). Airportia reported that while climbing through approximately 29,000 feet, its right-hand PW4090 engine emitted a loud bang, prompting the crew to shut it down and return to SFO. The aircraft landed safely on the same runway approximately one hour after departure. In both incidents, crews shut down the same engine model at similar altitudes, although no evidence has established a common technical cause.
United’s Boeing 777-200 fleet has experienced several other significant engine-related incidents over the past eight years. These have involved both Pratt & Whitney PW4000 engines and GE90s, showing the problems are not confined to one engine manufacturer. In June 2026, for example, a GE90-powered 777-200 operating from 
George Bush Intercontinental Airport (IAH) to 
Munich Airport (MUC) returned to its departure airport after passengers reported repeated bangs and flames from the right-hand engine. All these events ended with safe landings, but they illustrate the range of engine issues that can disrupt operations involving older widebodies.
Date
Aircraft
Engine
Incident
February 13, 2018
N773UA
PW4077
Fan blade failure over the Pacific, damaging the engine nacelle; landed safely in Honolulu.
February 20, 2021
N772UA
PW4077
Fan blade failure and engine fire after departing Denver; debris fell onto residential areas.
June 19, 2026
N78009
GE90
Repeated bangs and visible flames during departure from Houston; engine shut down.
July 9, 2026
N228UA
PW4090
Loud bang during climb from San Francisco; right engine shut down.
October 6, 2026
N796UA
PW4090
Severe vibrations and loud noises during climb; right engine shut down.
The most notorious incident occurred on February 20, 2021, when United UA328 suffered an uncontained engine-related debris event shortly after departing 
Denver International Airport (DEN) for Honolulu International Airport (HNL). A fractured fan blade damaged the right engine and nacelle, triggering a fire and sending debris falling onto neighborhoods in Broomfield, Colorado. The aircraft returned safely to Denver with no injuries among its 239 occupants.
The NTSB subsequently determined that fatigue failure of a fan blade was the probable cause, compounded by inadequate inspections and inspection intervals. The incident triggered widespread grounding and regulatory action affecting PW4000-powered 777s, and United later undertook modifications to return its aircraft to service.
Related
What was the reason behind the Star Alliance carrier’s decision?
Airlines Face Different Decisions Over Their Aging Boeing 777-200 Fleets
Credit: Markus Mainka | Shutterstock
Despite these incidents, United has a strong commercial incentive to retain its older widebodies. At the end of 2025, its fleet included 19 Boeing 777-200s averaging 28.5 years old, and 55 777-200ERs averaging 25.8 years, together representing substantial long-haul and high-density domestic capacity. United’s July 2026 fleet plan projected that all 96 of its 777s, including 22 newer 777-300ERs, would remain through year-end, even as its 787 fleet expanded from 85 to 100 aircraft. No firm retirement timetable has been announced for the 777-200 fleet, suggesting that the aircraft will continue playing an important role while newer Dreamliners support network growth.
Japan Airlines(JAL) adopted a very different strategy after experiencing its own serious 777-200 engine failure on December 4, 2020. JL904 suffered a Pratt & Whitney PW4074 fan-blade failure shortly after departing Okinawa, damaging the engine and aircraft before returning safely. Following United’s similar engine failure at Denver two months later, JAL grounded its 13 PW4000-powered 777s and accelerated their retirement to March 2021, according to Nippon.com. The airline cited economic considerations, with reduced pandemic-era demand and the availability of newer Airbus A350-900s making early retirement more practical.
Airline
777-200/200ER Fleet
Retirement Or Replacement Strategy
United Airlines
74
Continuing operations; no firm announced retirement date. Combined 777 fleet projected unchanged through 2026
Japan Airlines
Retired PW4000-powered domestic 777s in March 2021; last GE90-powered 777-200ER retired in 2023
American Airlines
47
Continuing operations and exploring cabin improvements; no planned near-term retirements
British Airways
43
Phased replacement of Gatwick-based 777-200ER aircraft with 787-10s beginning in 2029
American Airlines has even more reason to hold on to its older 777s. It operates 47 777-200ERs, and generally a smaller widebody fleet compared to United and 
Delta Air Lines following pandemic-era widebody retirements that it now likely regrets. So it’s not in a position to give up scarce long-haul capacity, and instead plans future cabin upgrades, indicating the type will fly with the airline for years to come.
British Airways has a clearer replacement pathway, with CEO Sean Doyle confirming that new 787-10s will begin replacing its Gatwick-based 777-200s in 2029. The British carrier’s aging fleet also came under scrutiny this past week when a nearly 30-year-old 777-200ER operating BA295 lost cabin pressure and descended rapidly over the Irish Sea before returning safely to Heathrow.
Although unrelated to United’s engine problems, the event further highlights the ongoing operational demands of maintaining first-generation 777s approaching their fourth decade of service. Aircraft age alone does not establish declining safety, but the economics of maintaining these increasingly elderly jets will inevitably influence how long they remain in service.