Alaska Airlines Flight 73
Boeing 737-4Q8 · Incident: cabin safety event en route
From Sitka Rocky Gutierrez Airport (PASI) to Juneau International Airport (PAJN)
Event
- NTSB case
- ANC09IA015
- 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
- Visual Meteorological Cond
Boeing 737-4Q8
- 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
- N771AS
- Operator
- Alaska Airlines
- Onboard fatalities
- Unknown
- Route
- From Sitka Rocky Gutierrez Airport (PASI), Sitka, AKTo Juneau International Airport (PAJN), Juneau, AK
- 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 · climb to cruise
- 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
- Cabin safety event
- 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
- Aircraft › Aircraft handling/service
- Personnel issues › Task performance
Approximate · Coordinates from the NTSB case API, which marks them as estimated or does not say; no uncertainty radius is established.
NTSB narrative
After departure the cabin crew reported to the captain that they were becoming nauseated. The captain noted that the departure was the first flight of the day and that the airplane had been sitting on the ramp overnight connected to an external heating unit. He said that prior to flight the first officer and cabin crew went to prepare the airplane while he remained in the operations center with paperwork. He said the first officer requested the ground crew shutdown the external heater because of exhaust fumes in the airplane's cabin. The first officer started the airplane's auxiliary power unit to provide power and heat to the airplane. The captain said that about 15 minutes later he did not detect any unusual smells or odors, and wiped his hand across seats and surfaces to detect contamination. Finding none, he felt it was safe to continue boarding. He reported that the boarding process was normal, and none of the crew or passengers reported any unusual smells or odors. When the cabin crew reported feeling nauseated, the captain determined that they were 20 minutes from their destination and decided to continue the flight rather than turn back. The captain reported that he and the first officer were symptom free, and that the first officer remained on oxygen for the remainder of the flight as a precaution. Upon arrival the flight crew all tested positive for elevated levels of carbon monoxide. The cabin of the airplane was examined and no traces of carbon monoxide were found. Tests of the ground heating unit found no anomalies, and the heat output hose was tested for CO with negative results. According to the director of safety for the operator, the contamination probably occurred when the morning ground crew started the push-back unit in the proximity of the heater's fresh air intake. As a result, the heating unit has been repositioned away from other operating equipment, and a 20-foot exhaust hose attached. Carbon monoxide detectors are now placed in the operator's aircraft during extended external heater usage.
Probable cause
The placement of operating equipment in close proximity to an external heating unit's intake by ground personnel, resulting in the contamination of the airplane's cabin with carbon monoxide.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record ANC09IA015
- Event ID
- 20081223X70710
- Case number
- ANC09IA015
- 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, 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: 10798ec318fa987f49cf7cc4d5e67a1f090dc7ceff451d0c645efece697a5a8a; retrieved 2026-09-15T10:37:53.031Z.