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| Date: | Sunday 28 September 2025 |
| Time: | 18:11 |
| Type: |  Boeing 777-222ER |
| Owner/operator: | United Airlines |
| Registration: | N788UA |
| MSN: | 26942/82 |
| Year of manufacture: | 1997 |
| Engine model: | P&W PW4090 |
| Fatalities: | Fatalities: 0 / Occupants: 284 |
| Other fatalities: | 0 |
| Aircraft damage: | None |
| Location: | London Heathrow Airport -
 United Kingdom
|
| Phase: | En route |
| Nature: | Passenger - Scheduled |
| Departure airport: | London-Heathrow Airport (LHR/EGLL) |
| San Francisco International Airport, CA (SFO/KSFO) | |
| Confidence Rating: |  Information is only available from news, social media or unofficial sources |
United Airlines flight UA939, a Boeing 777-222ER (N788UA), operating from London Heathrow (LHR) to San Francisco (SFO), returned to Heathrow shortly after departure following reports of severe airframe and engine vibrations.
The aircraft departed LHR at 16:21 BST (15:21 UTC) and was cruising at FL310 over northwestern England when the flight crew detected significant vibrations. The crew declared an emergency (squawk 7700) and entered a holding pattern near Blackpool to troubleshoot the issue. As a precaution, the left-hand engine (Pratt & Whitney PW4090) was shut down after the vibrations persisted.
The aircraft jettisoned fuel to reduce landing weight before returning to Heathrow, where it landed safely on Runway 27L at 18:11 BST (17:11 UTC). Emergency services met the aircraft on arrival, and passengers disembarked normally. There were no injuries among the 284 occupants.
Post-flight inspections revealed no visible damage to the aircraft. United Airlines confirmed a mechanical issue as the cause of the precautionary return. The aircraft remained grounded for maintenance checks following the incident.
Sources:
https://avherald.com/h?article=5184c5aa
https://www.reddit.com/r/flightradar24/comments/1nssfzc/united_airlines_emergency_over_the_uk/
https://simpleflying.com/united-airlines-boeing-777-london-heathrow-return-engine-issue/
https://www.flightradar24.com/data/flights/ua939
https://www.flightaware.com/live/flight/UAL939/history/20250928/1525Z/EGLL/EGLL
History of this aircraft
Other occurrences involving this aircraft
| 10 February 2024 | N788UA | United Airlines | 0 | near Kelsey, NY |  |
non |
| Turbulence | ||||||
| 30 September 2024 | N788UA | United Airlines | 0 | 148 nm NW of Calgary, AB |  |
non |
| Fumes/smoke/odor event | ||||||
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 10-Oct-2025 17:04 | Luxa | Added |
| 10-Oct-2025 17:27 | ASN | Updated [Source, ] |
Corrections or additions? ... Edit this accident description
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