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| Date: | Thursday 22 May 2025 |
| Time: | 09:49 PDT |
| Type: |  Boeing 737-790 (BDSF) (WL) |
| Owner/operator: | Alaska Airlines |
| Registration: | N627AS |
| MSN: | 30794/796 |
| Year of manufacture: | 2001 |
| Engine model: | CFMI CFM56-7B |
| Fatalities: | Fatalities: 0 / Occupants: |
| Other fatalities: | 0 |
| Aircraft damage: | Unknown |
| Location: | 17 nm SE of Comox, BC -
 Canada
|
| Phase: | En route |
| Nature: | Cargo |
| Departure airport: | Seattle/Tacoma International Airport, WA (SEA/KSEA) |
| Juneau International Airport, AK (JNU/PAJN) | |
| Investigating agency: | TSB |
| Confidence Rating: |  Information verified through data from accident investigation authorities |
Alaska Airlines flight AS7040, a Boeing 737-790, suffered pressurization issues in the vicinity of Comox, BC, Canada.
Shortly after levelling at an altitude of approximately 40 000 feet above sea level (ASL), the aircraft cabin altitude warning annunciation illuminated, and the accompanying warning horn sounded. The flight crew donned their oxygen masks and accomplished the quick reference checklist (QRC). The flight crew then declared an emergency with air traffic control (ATC) and requested a lower altitude. A rapid descent to 10 000 feet ASL was made approximately 17 nautical miles southeast east of Comox Airport (CYQQ), BC. The flight then diverted back to Seattle/Tacoma International Airport, WA (SEA) and landed without further incident. No injuries were reported.
Maintenance personnel accomplished a built-in test (BIT) check of the No. 1 Digital Cabin Pressure Control System (DCPCS) which revealed fault code 107. The aircraft’s aft outflow valve assembly and cabin pressurization controller module were replaced to rectify the fault. Operational checks were performed, and the aircraft was returned to service.
Sources:
TSB A25P0064
History of this aircraft
Other occurrences involving this aircraft
| 25 July 2004 | N627AS | Alaska Airlines | 0 | Gustavus Airport, AK (GST/PAGS) |  |
min |
| Collision with Ground support equipment | ||||||
| 25 July 2021 | N627AS | Alaska Airlines | 0 | 56 nm WNW of Nanaimo, BC | |
non |
| Loss of pressurization | ||||||
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 16-Jul-2025 18:31 | ASN | Added |
| 16-Jul-2025 18:34 | ASN | Updated [Aircraft type, Cn, Location, Phase, Nature, Narrative, ] |
| 16-Jul-2025 18:34 | ASN | Updated [Cn, ] |
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