Later, an official encouraged him to land the plane, to which the man replied: "I don't know, man". The mechanic was either "doing stunts in air" or "his lack of flying skills caused crash into [Ketron] Island".
Air traffic controllers and pilots could be heard discussing a "ground stop" and dealing with a backlog of aircraft. Witnesses shared footage of the plane's erratic flight before it crashed in Pierce County around 8:45 p.m.
Then the passenger plane pilot "did a complete loop".
Alaska Air said the F-15s were scrambled from a Portland air base.
The pilot's condition is not yet known, but police say the "fiery crash" made it likely that it was "probably not a good condition".
Mr Troyer said that he is working with Federal Bureau of Investigation and military personnel as they investigate what happened.
"My husband and I are recently former Boeing employees and we were wondering why a jet was near the passenger airplane", she said.
Alaska Airlines confirmed that a Horizon Air Q400 was involved in an "unauthorized take-off" in a tweet.
Royal King told The Seattle Times he was photographing a wedding when he saw the low-flying turboprop being chased by two F-15s.
It added: "This is not a terrorist incident". This individual who took the aircraft, who has not yet been positively identified until remains are examined, is believed to have been the only person on the plane when the plane was taken from a maintenance position at Sea-Tac. According to ABC news, the plane had to be diverted away from the city by US Air Force fighter jet after it took off from Sea-Tac International Airport.