New Delhi, Feb. 1 -- A supervisor allegedly allowed an aircraft traffic controller at Ronald Reagan Washington National Airport to leave early, hours before a fatal, mid-air collision between a Black Hawk helicopter of the US Army and an American Airlines passenger aircraft on Wednesday.

The supervisor's action meant only a single air traffic controller was managing both plane and helicopter traffic when there should have been two people monitoring the flight paths, the report said.

The two aircraft plunged into the icy Potomac river shortly before 9 pm local time (Thursday, 7:30 am IST). All 64 passengers on the American Airlines regional jet and the three soldiers on the Black Hawk, are presumed dead.

The Federal Aviation Authority (...