Shortly before the collision, air traffic controllers at Reagan National Airport asked the pilots of the military helicopter if they had the arriving regional jet in sight, according to an audio recording.

After the transmission, the controller gives the helicopter permission to pass behind the jet.

The helicopter pilots acknowledge that the regional jet is in sight and that they will “maintain visual separation,” according to the audio recording.

The two aircraft collide shortly after the tower controller’s radio call.

A pilot from another aircraft is heard saying, “Tower, did you see that?”

The air traffic controller is then heard frantically diverting other arriving aircraft away from the airport.