USAir Flight 93
Boeing 737-3B7 · Incident: airframe, component or system failure en route
From Philadelphia International Airport (PHL) to Fort Lauderdale Hollywood International Airport (FLL)
Event
- NTSB case
- MIA95IA214
- 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
- 0
- 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 737-3B7
- Aircraft type
- Boeing 737
- 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
- N373US
- Operator
- USAir
- Onboard fatalities
- Unknown
- Route
- From Philadelphia International Airport (PHL), Philadelphia, PATo Fort Lauderdale Hollywood International Airport (FLL)
- 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
- En route · descent
- First occurrenceThe 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
- Airframe, component or system failure
- 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
- Autopilot/flight director, servo › Other
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
THE FLIGHT EXPERIENCED AN UNCOMMANDED ROLL TO THE RIGHT DURING DESCENT FOR LANDING. THE 'B' AUTOPILOT SYSTEM WAS ENGAGED AT THE TIME. POST INCIDENT EXAMINATION SHOWED THE 'B' AUTOPILOT AILERON ACTUATOR HAD LOW ELECTRICAL RESISTANCE. TESTS BY BOEING COMMERCIAL AIRPLANE COMPANY HAVE SHOWN THAT LOW ELECTRICAL RESISTANCE WITHIN THE AUTOPILOT AILERON ACTUATOR WILL CAUSE UNCOMMANDED ROLL OCCURRENCES.
Probable cause
LOW ELECTRICAL RESISTANCE OF THE AUTOPILOT AILERON ACTUATOR FOR UNSPECIFIED REASONS WHICH RESULTED IN AN UNCOMMANDED ROLL TO THE RIGHT.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record MIA95IA214
- Event ID
- 20001207X04318
- Case number
- MIA95IA214
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
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: 1fe41f13a32ef9ab864c8116a5197723fe4ac817e8d9864fc485b647f07d9d30; retrieved 2026-09-18T17:57:48.835Z.