CBS News has independently confirmed one air traffic controller was doing the job normally handled by two when a passenger jet and a Black Hawk helicopter collided in midair Wednesday night and crashed into the Potomac River near Reagan National Airport and Washington,

Amid increased concerns about aviation safety, here's how many air traffic controllers there are in the U.S., and how the hiring process works.

One widely shared claim was that Trump fired 3,000 air traffic controllers shortly after taking office for his second term. One post alone (archived) making this claim had received more than 2.7 million views and 25,