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| Date: | Tuesday 2 September 2025 |
| Time: | 12:20 UTC |
| Type: |  Boeing 757-26D (WL) |
| Owner/operator: | Delta Air Lines |
| Registration: | N821DX |
| MSN: | 33961/1046 |
| Year of manufacture: | 2004 |
| Fatalities: | Fatalities: 0 / Occupants: 190 |
| Other fatalities: | 0 |
| Aircraft damage: | None |
| Location: | 108 nm N of Natashquan, Quebec -
 Canada
|
| Phase: | En route |
| Nature: | Passenger - Scheduled |
| Departure airport: | Keflavík International Airport (KEF/BIKF) |
| Detroit-Metropolitan Wayne County Airport, MI (DTW/KDTW) | |
| Investigating agency: | TSB |
| Confidence Rating: |  Information verified through data from accident investigation authorities |
Delta Airlines flight DL179, a Boeing 757-200, was on an instrument flight rules flight from Keflavik Airport, Iceland to Detroit Metropolitan Wayne County, USA. At 12:20 UTC about 108 nautical miles (nm) north of Natashquan (CYNA), Quebec, the crew noticed that the temperature in the cockpit was warmer, so they adjusted the left pack and shortly afterwards the right pack failed, followed by the left 30 seconds later. The crew donned the oxygen masks and declared an emergency due to a pressurisation problem, carried out an emergency descent to 10,000 feet and requested a diversion to Montreal/Pierre Elliott Trudeau International Airport, QC (YUL). During the descent, passing FL280, the cabin altitude exceeded 14,000 feet and the masks deployed automatically in the cabin. During the diversion, the right-hand pack resumed operation, but the left-hand pack did not. The aircraft landed safely at YUL.
Sources:
TSB A25Q0139
https://www.flightradar24.com/data/aircraft/n821dx#3c045481
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 10-Sep-2025 18:19 | ASN | Added |
| 10-Sep-2025 18:22 | ASN | Updated [Aircraft type, Cn, Total occupants, Location, Phase, Nature, Departure airport, Source, Damage, Narrative, ] |
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