U.S. investigators are examining whether two airline flights landed at Ronald Reagan Washington National Airport today without tower guidance because the lone controller on duty was asleep.

The American Airlines and United planes landed safely at about 12:10 a.m. and 12:25 a.m., respectively, Peter Knudson, a spokesman for the National Transportation Safety Board, said in an interview.

Pilots of the American plane aborted a first landing attempt when no one in the tower responded to calls and then landed without assistance, Knudson said. The United pilots landed the first time, and crews from both planes treated the airport the same as one that doesn’t ordinarily have controllers in early morning hours, he said.

There was one controller working in the Reagan tower at the time, Knudson said. The board doesn’t yet know why the worker didn’t respond to calls and is looking into the possibility the controller was asleep, he said. The planes were in contact with controllers at a regional center in Virginia, he said.

Shortly after the United flight landed, the tower was responsive, Knudson said.

The Federal Aviation Administration declined to say whether the controller was asleep or whether any action was taken against the worker. “The FAA is looking into staffing issues and whether existing procedures were followed appropriately,” agency spokeswoman Laura Brown said.

United is also investigating, Megan McCarthy, a spokeswoman for the airline, said. She referred questions to the NTSB. The flight was an Airbus SAS A320 carrying 63 passengers and five crew members from Chicago’s O’Hare airport, she said.

(Source: Bloomberg)