WASHINGTON — The administration of US President Donald Trump has begun firing several hundred Federal Aviation Administration employees, upending staff members on a busy air travel weekend and just weeks after a fatal midair collision at the Ronald Reagan Washington National Airport.

Probationary workers were targeted in late-night emails on Friday notifying them that they had been fired, David Spero, president of the Professional Aviation Safety Specialists union, said in a statement.

The impacted workers include personnel hired for FAA radar, landing and navigational aid maintenance, one air traffic controller told The Associated Press.

In a message posted on X late Monday, US Transportation Secretary Sean Duffy said fewer than 400 FAA employees were fired and that "zero air traffic controllers and critical safety personnel were let go".

The firings hit the FAA as it is facing a shortfall in controllers. Federal officials have been raising concerns about an overtaxed and understaffed air traffic control system for years, especially after a series of close calls between planes at US airports. Among the reasons they have cited for staffing shortages are uncompetitive pay, long shifts, intensive training and mandatory retirements.

In the Jan 29 fatal collision between a US Army Black Hawk helicopter and an American Airlines passenger jet, which is still under investigation, one controller was handling both commercial airline and helicopter traffic at the busy airport.

Crash landing

In the latest setback to US aviation, a Delta Air Lines regional jet flipped upside down upon landing at Canada's Toronto Pearson Airport on Monday amid windy weather following a snowstorm, injuring 18 of the 80 people on board, officials said.

Three people on flight DL4819 from Minneapolis-St Paul International Airport suffered critical injuries, among them a child, a Canadian air ambulance official said, with 15 others also immediately taken to hospitals.

Some of the injured have since been released, Delta said late on Monday.

The US carrier said a CRJ900 aircraft, operated by its Endeavor Air subsidiary, was involved in an accident with 76 passengers and four crew members on board.

The 16-year-old CRJ900, made by Canada's Bombardier and powered by GE Aerospace engines, can seat up to 90 people. At least one of the two wings was no longer attached to the plane, a post-accident video showed.

Canadian authorities said they would investigate the cause of the crash, which was not yet known.

Agencies Via Xinhua