The control tower at Reagan National Airport is seen in Arlington, Wednesday. Federal safety officials are investigating a report that two planes landed at the airport without control tower clearance becasue the air traffic controller was asleep. Cliff Owen/Associated Press

Air traffic safety is under increased scrutiny by federal authorities following an incident in which two passenger jets landed without controller assistance at Reagan National Airport because no one could be reached in the airport tower.

An aviation official said that an air traffic supervisor — the lone controller on duty around midnight on Tuesday when the incident occurred — had fallen asleep.

Transportation Secretary Ray LaHood LaHood directed the Federal Aviation Administration to launch a nationwide inquiry into airport tower staffing issues.

Peter Knudson, a spokesman for the National Transportation Safety Board, said Wednesday that the pilots of the two planes were in contact with controllers at a regional FAA facility about 80 kilometres away in Warrenton, Va.

He said that after pilots were unable to raise the airport tower at Reagan by radio, they asked controllers in Warrenton to call the tower. Repeated calls from the regional facility to the tower went unanswered, Knudson added.

In response to the incident, LaHood told the FAA to put two air traffic controllers on the midnight shift at Reagan.

"It is not acceptable to have just one controller in the tower managing air traffic in this critical air space," LaHood said. Reagan National is located in Northern Virginia just across the Potomac River from Washington.

The planes involved were American Airlines flight 1012, a Boeing 737 with 91 passengers and 6 crew members on board, and United Airlines flight 628T, an Airbus A320 with 63 passengers and five crew members.