The theft of an empty plane by an airline worker who performed dangerous loops before crashing into a remote island in Puget Sound illustrated what aviation experts have long known: One of the biggest potential perils for commercial air travel is airline or airport employees causing mayhem.

"The greatest threat we have to aviation is the insider threat," said Erroll Southers, a former FBI agent and transportation security expert. "Here we have an employee who was vetted to the level to have access to the aircraft and had a skill set proficient enough to take off with that plane." Video showed the Horizon Air Q400, a turboprop plane that seats 76 people, doing large loops and other dangerous maneuvers as the sun set on Puget Sound. The flight lasted about 75 minutes, and ended Friday night when he crashed into the small island after being chased by military jets. The two F-15C aircraft scrambled from Portland didn't fire the plane, authorities said. Southers said the man could have caused mass destruction.