An air traffic control supervisor allowed an employee on Wednesday to leave their shift early, which meant another controller allegedly handled two jobs on the day of the fatal plane collision at Ronald Reagan Washington National Airport, NBC News reported Friday.

An American Airlines flight collided with a military Blackhawk helicopter on Wednesday, killing all 64 people on board the plane, and three people on the helicopter. 

The incident occurred after one controller covered both plane and helicopter traffic in the area, according to a preliminary Federal Aviation Administration report. The staffing was unusual for the time of day. Normally, one controller is dedicated to helicopters while another controller handles planes, per NBC. But the supervisor allowed one employee to leave the job early for an unknown reason.

There are times when only one controller handles both helicopter and plane air traffic, but it does not usually take place until 9:30 p.m. when traffic is slower, per the New York Post. The crash occurred around 8:53 p.m., according to Washington, D.C Police.

The lone controller told the helicopter that it was flying too close to an airplane and told it to avoid the plane, according to the Post, but the controller did not give the exact location of the plane and the helicopter could have been trying to dodge a different plane that was taking off nearby. 

The National Transportation Safety Board is also looking into whether the helicopter was flying too high at the time of the collision. The exact cause of the incident is not known.

Misty Severi is a news reporter for Just The News. You can follow her on X for more coverage.