UNITED AIRlNES Flight 909
Boeing 757-222 · Incident: birdstrike during landing
From Chicago O'Hare International Airport (ORD) to Denver International Airport (DEN)
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
- ENG11IA051
- 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
- Incident
- 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
- Not recorded
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
- N526UA
- Operator
- UNITED AIRlNES
- Onboard fatalities
- Unknown
- Route
- From Chicago O'Hare International Airport (ORD), Chicago, ILTo Denver International Airport (DEN), Denver, CO
- 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
- Landing · landing roll
- 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
- Birdstrike
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Minor
Cause areas
- Environmental issues › Physical environment
Approximate · Coordinates from the NTSB case API, which marks them as estimated or does not say; no uncertainty radius is established.
NTSB narrative
On September 26, 2011, 1637 mountain daylight time, a Boeing B-757-222, registration number N526UA, operated by United Airlines (UAL) as flight 909, and powered by two Pratt & Whitney PW2037M turbofan engines, experienced a left engine (No. 1) bird strikeF following touchdown on runway 35R at the Denver International Airport (DEN), Denver, Colorado. According to the flightcrew, after initial touchdown and the application of full reverse thrust, two hawks were observed on the centerline of runway 35R and shortly thereafter impacts were felt on the fuselage. The airplane was towed to the gate using a tug where the passengers deplaned normally. The incident flight was a 14 CFR Part 121 domestic passenger flight from Chicago O’Hare Airport (ORD) to DEN.
Examination of the airplane revealed only minor gouging of the fuselage while the No. 1 engine inlet cowl exhibited multiple impacts, gouges, and through-holes. Examination of the No. 1 engine revealed that all the fan blades were extensively damaged, three fractured transversely across the airfoil at or near the mid-span shroud, but no penetration or breaches were observed in any of the engine cases. The bird remains recovered within the No. 1 engine were identified as coming from a female Red-Tailed Hawk. An intact bird that struck the side of the No. 1 inlet was also identified as a Red-Tailed Hawk but was not sexed.
Comparing the airplane and engine damage to the requirements for bird ingestion and engine debris containment at the time the engine and airplane were both certificated revealed that the engine complied with the bird ingestion and containment requirements set forth in Parts 33.77 and 33.19 and the airplane complied with the containment requirements set forth in Parts 25.903.
Probable cause
**This probable cause was modified on 4/5/2012. Please see the public docket for this accident to view the original probable cause.**
The initial damage to the fan blades was caused by the ingestion of a Red-Tailed Hawk that caused one or more fan blades to fracture, striking the fan case and causing it to bulge. The initial fan blade fragment release impacted and damaged other passing fan blades generating various sized blades fragments. Some of these blade fragments were propelled forward of the fan case by passing fan blades and were reingested, creating a cascading effect of collateral impact damage to the other fan blades, the fan case, and the inlet cowl.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record ENG11IA051
- Event ID
- 20110927X91721
- Case number
- ENG11IA051
- 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, coordinates. 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: 96281dbbff6fe2cf413b01d5a82d4636540eccbd1b1cffb4eaf072feb2bbaa00; retrieved 2026-09-15T16:47:08.668Z.