The Federal Aviation Administration fired fewer than 400 employees out of its workforce of 45,000, Transportation Secretary Sean Duffy said on Monday, as questions rise around air traffic safety amid a spate of recent plane accidents.

Several hundred new support staff employees at the Federal Aviation Administration have been fired as part of the Trump administration's terminations of federal workers, according to their union.

Staff cuts hit employees who support aviation safety and security operations as the agency is grappling with a series of airplane crashes.

The firings hit the FAA as federal officials have been raising concerns about an overtaxed and understaffed air traffic control system for years.

Nearly 300 Federal Aviation Administration employees were fired just weeks after a midair collision over Washington, D.C., killed 67 people.