UPDATE 2-Air controller slept as planes landed in Washington

* Lone tower controller says he was asleep, is suspended

* Two planes land safely, not in danger, FAA says

* Safety board looking closely at controller performance (Adds tower staffing, other incidents, controller errors)

By John Crawley

WASHINGTON, March 24 (Reuters) - An air traffic controller told U.S. investigators on Thursday he had fallen asleep on the job, leaving two jetliners to land in Washington without any airport guidance.

"As a former airline pilot, I am personally outraged that this controller did not meet his responsibility to help land these two airplanes," Randy Babbitt, the Federal Aviation Administration administrator, said in a statement.

Babbitt, who suspended the unidentified 20-year veteran, is reviewing the incident, which occurred early Wednesday, along with the National Transportation Safety Board (NTSB).

The two flights -- one operated by United Airlines (UAL.N) and the other by American Airlines AMR.N -- landed without incident at Ronald Reagan National Airport early Wednesday.

Flight crews could not raise the airport tower on the radio for runway and landing instructions shortly after midnight but were in contact with another nearby FAA facility.

"Fortunately, at no point was either plane out of radar contact and our back-up system kicked in to ensure the safe landing of both airplanes," Babbitt said.

The controller, a supervisor, told NTSB investigators who interviewed him he fell asleep for a period of time on duty, the board said in a preliminary report on the incident.

The controller told the NTSB it was his fourth straight overnight shift and he was alone in the tower. Radio contact was lost for more than 20 minutes, the NTSB said.

The incident at the airport in the shadow of the Pentagon and across the Potomac River from the White House upset official Washington, which is sensitive to any lapse in aviation operations since the Sept. 11, 2001, hijack attacks. A small plane crashed into the White House grounds in 1994.

Flights at National are heavily regulated and the airport closes earlier than other big centers because of noise restrictions. There are only a handful of scheduled flights after midnight on most nights, fewer on others.

The FAA is looking at overnight controller staffing issues nationwide. About 30 towers operate with just one controller after midnight. Most major centers, including Chicago O'Hare, LaGuardia and Kennedy in New York, Boston and Washington Dulles, operate with at least two controllers.

The safety board has in recent months stepped up its review of controller staffing, performance and fatigue issues. This includes the near miss of a passenger jet and two military aircraft in January over the Atlantic Ocean off New York.

Suspected controller errors in 2010 hit 1,887 from 1,233 the previous year, according to the FAA. More than half were considered relatively minor but reports in the most severe category rose from 37 to 43, FAA figures show. (Reporting by John Crawley; editing by Todd Eastham)