The FAA says a controller at Seattle's Boeing Field was let go on Monday after being caught sleeping on duty on two different occasions.
This comes after two other air traffic controllers were recently fired for sleeping on the job. Since March, five incidents of sleeping on the job have surfaced, along with one of an air controller watching a DVD movie while on the overnight shift and an aborted landing of a plane with first lady Michelle Obama and Jill Biden, wife of the vice president, on board.
U.S. Transportation Secretary Ray LaHood says safety is his department's highest priority.
The Associated Press contributed to this report.