United Airlines Boeing 757-222 accident
Boeing 757-222 · Accident: turbulence encounter on approach
From Denver International Airport (DEN) to San Francisco International Airport (SFO)
Narrative check · The NTSB narrative appears to contradict this record's location. Values are shown as recorded, not corrected; compare with the narrative.
Event
- NTSB case
- WPR12LA057
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Accident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- API-reported fatalities
- 0 · all aircraft and ground
- Ground fatalities
- Unknown
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- Airline
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
Boeing 757-222
- Aircraft type
- Boeing 757
- Category
- Airplane
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N547UA
- Operator
- United Airlines
- Onboard fatalities
- Unknown
- Route
- From Denver International Airport (DEN), Denver, COTo San Francisco International Airport (SFO), San Francisco, CA
- Aircraft age
- Not recorded
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Part 121: Air Carrier
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- Approach · IFR initial approach
- Defining eventThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- Turbulence encounter
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- None
Cause areas
- Environmental issues › Conditions/weather/phenomena
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
While en route at flight level (FL) 360, the captain of the commercial air carrier flight requested and was granted a lower altitude (FL 300) to minimize the effect that turbulence was having on the airplane. After the captain received pilot reports indicating that varying degrees of turbulence, mountain wave activity, and low-level windshear existed, he illuminated the seat belt sign and made an announcement for the passengers to be seated. The flight crew then advised the cabin crewmembers of possible turbulence and instructed them to prepare the cabin for landing, stay near their seats, and be seated immediately if turbulence was encountered. About 7 to 10 minutes later, while the airplane was at FL 300, the flight encountered moderate-to-severe turbulence. A flight attendant who was in the lavatory when the turbulence was encountered sustained a broken ankle after being thrown in the air twice.
Probable cause
The flight's encounter with known severe turbulence associated with mountain wave activity, which resulted in a flight attendant sustaining a broken ankle.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record WPR12LA057
- Event ID
- 20111208X41332
- Case number
- WPR12LA057
- Dataset
- full-current
- Source SHA-256
- 5cf380f0061817c0331a6b2d8cc7e0ee3a79bea469a1001dc5c10e56f35f5ab3
Source notes (4)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status, damage. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: ea5c266e8fceba2d5133b02a128d01d8d0c419e037ae45ce1514f148492a2514; retrieved 2026-09-15T16:59:54.625Z.