Boeing 737-4Q8 incident near Sitka, Alaska, December 20, 2008
On December 20, 2008 at about 11:47 am local time, a Boeing 737-4Q8, registered N771AS, was involved in an incident during enroute (climb to cruise) near Sitka, Alaska (Sitka airport). It was flown under scheduled airline rules (Part 121). 88 people had minor injuries. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
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.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- December 20, 2008 · about 11:47 am local time
- Place
- Sitka, Alaska · Sitka · map
- Type
- Incident
- Injuries
- 88 people had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft
- Boeing 737-4Q8 · all 737-4Q8s on the register
- Registration
- N771AS · no longer on the register · serial 25104
- Damage
- Not recorded
- Flight
- Flight · scheduled airline rules (Part 121)
The NTSB's narrative final · quoted from the NTSB record
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.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
What happened, in order
- Cabin safety event during prior to flight
- Cabin safety event during enroute (climb to cruise) defining event
The NTSB's findings
- cause Aircraft › Aircraft handling/service › (general) › (general) › Incorrect service/maintenance
- cause Personnel issues › Task performance › Use of equip/info › Use of equip/system › Ground crew
Pilot
- Certificate: airline transport pilot
- Ratings: multi-engine land; single-engine land
- Flight time: 12,100 hours in all
- Medical certificate: Class 1
- Injury: no injuries
The aircraft
- Seats: 149
- Landing gear: retractable
- Engine 1: Cfm Intl. CFM56 SERIES (turbofan); 0 hours total
- Engine 2: Cfm Intl. CFM56 SERIES (turbofan); 0 hours total
- Operator: Alaska Airlines
The flight
- Departed from: PASI Sitka AK at 12:30 pm
- Destination: PAJN Juneau AK
- Flight plan: IFR
- A second pilot was aboard
Weather at the time
- Light: night
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 0°F (-18°C), dew point 0°F (-18°C)
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Cabi | 3 | |||
| Flight crew | 2 | |||
| Passengers | 83 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.