United Airlines Grounded 777 After Engine Shutdown

A United Airlines Boeing 777-200ER has been grounded for multiple days after it was forced to return to San Francisco following a loud bang and engine shutdown mid-flight.

The Boeing 777 flying with the U.S. carrier has been involved in a string of incidents in recent years, with the ageing fleet a persistent recipe for reliability disasters. This is the latest in a string and was flagged by The Aviation Herald.

The Boeing 777 landed safely, but it was not reaching its intended destination, Frankfurt, raising further questions about the long-term reliability of the engines and the aircraft as investigations into the problems commenced.

What Happened On UA926?

A Boeing 777-200ER operated flight UA926 on a service between San Francisco and Frankfurt, where it was climbing after departure, before passengers heard a loud bang from the right engine and the cabin lights began to flicker.

The crew then stopped the climb aboard the aircraft, shut down the Pratt & Whitney PW4090 engine, and returned to San Francisco, landing safely on runway 28R about 1 hour after takeoff.

A replacement Boeing 777-200ER was then dispatched to safely deliver passengers to Frankfurt with a near 6-hour delay once all was said and done following the initial incident aboard UA926.

N228UA was the aircraft involved in the incident. The aircraft was grounded until 12 July 2026, when it returned to scheduled passenger flights on UA58 between San Francisco and Frankfurt with a 1405 departure. This aircraft is 24.5 years of age and has only ever flown with the U.S carrier following a February 2002 delivery.

A Pattern On The Boeing 777 With United

United Airlines operates a large number of early-built Boeing 777-200ERs, with many of them delivered in the latter stages of the 1990s and powered by Pratt & Whitney’s PW4000 family. This combination has, over the years, been a problem child with recurring incidents such as these, some more severe in nature.

In February 2021, a United Airlines flight from Denver to Honolulu, UA328, experienced an uncontained failure of a PW4077, resulting in debris over a Denver suburb and an emergency landing. Later investigations led by the NTSB found inadequate inspection intervals and that a missed fan-blade crack contributed to the failure, leading to the grounding of these powered 777s for inspections.

Then, four years later, in May 2025, a United Airlines 777 operating UA889 from Beijing had to reject takeoff after a loud bang and a visible fire from the right PW4090 engine. Later, the engine failure was identified with several tyres bursting and the jet being stood down.

The string of 2025 incidents would continue when, one month later, UA803 from Washington, D.C., would be forced to return to its airport of origin after takeoff due to severe overheating in the right PW4090.

In September 2025, another 777-200ER was forced to return to London Heathrow during a routine flight to San Francisco after an abnormal airframe vibration prompted a precautionary shutdown of the PW4090 engine.

These incidents, in such a short space of time and involving the Pratt & Whitney engine on the same aircraft variant, are extremely rare. As such, it prompted the airline’s CEO, Scott Kirby, to publicly address the issue, maintenance, and processes.

The PW4000 series isn’t new, and over the years, several airworthiness directives and service bulletins have addressed fan blade cracking due to metal fatigue, as well as thermal-acoustic inspection requirements and inspection intervals for rotating parts. With the more recent incidents, this decade has been marked by heightened scrutiny.

As for the UA926 incident this month that forced a United Airlines 777-200ER to return to San Francisco, details on what was specifically identified have yet to come to light, as investigations are required. The jet, however, has safely returned to service after spending some time on the ground.