(I couldn't get the initial emergency declaration, coverage from that sector of Salt Lake (ZSL06) not great, but here's the rest)
An Alaska Airlines Boeing 737-900, registration N215AK performing flight AS-360 from Seattle,WA to Tampa,FL (USA), was enroute at FL350 about 160nm northeast of Boise,ID (USA) when the crew donned their oxygen masks reporting smoke in the cockpit and decided to divert to Boise. Descending through about 14,000 feet the crew advised the smoke was increasing. The aircraft landed without further incident on runway 10R about 35 minutes after deciding to divert and taxied to the apron.
The remainder of the flight and the rotation was cancelled.
The aircraft remained on the ground in Boise for about 45 hours, then positioned to Seattle but has not yet returned to service about 84 hours (3 days 12 hours) after landing in Boise.
A passenger reported there was a smell like gas in the cabin, the engine power was reduced, the oxygen masks were released and the aircraft descended. Another passenger saw sparks and small flames outside.
https://flightaware.com/live/flight/ASA360/history/20240714/0425Z/KSEA/KTPAhttps://avherald.com/h?article=51b3548f&opt=0