SEATTLE • Federal authorities were searching yesterday for what drove an airline worker to steal an empty aircraft from Seattle's airport and crash it into a nearby sparsely populated island, sparking a security scare that saw US fighter jets scrambled.

A Horizon Air ground service agent took the controls of a Bombardier Q400 turboprop aircraft in a maintenance area at Seattle-Tacoma International Airport at about 8pm local time on Friday (11am Singapore time yesterday) and took off, embarking on a flight over Seattle before crashing about an hour later on Ketron Island in Puget Sound, Horizon sister carrier Alaska Airline said online.

The 29-year-old man, who has not been identified, was suicidal and appeared to have acted alone, the Pierce County Sheriff's Department said on Twitter, adding that the employee was probably killed in the crash.

"Doing stunts in air or lack of flying skills caused crash into Island," the sheriff said on Twitter.

The Federal Aviation Administration, Federal Bureau of Investigation and National Transportation Safety Board were investigating the incident, said Mr Brad Tilden, Alaska Air Group chief executive. "We're working to find out everything we possibly can about what happened," he said.

There was no indication that the incident was an act of terror and no passengers were aboard the aircraft, the FBI said in a series of tweets.

REUTERS