The Trump administration has begun firing several hundred Federal Aviation Administration employees, upending staff on a busy air travel weekend and just weeks after a fatal mid-air collision in Washington.

Emails to air-traffic controllers, according to a second air-safety union president, came “from an ‘exec order’ Microsoft email address” — not a government email address.

A union representing air safety personnel said it’s reviewing the fallout from a slew of firings late Friday with the Federal Aviation Administration.