In the dead of night, the air traffic control tower at Tucson International Airport is one of the loneliest places in town.
One person works the graveyard shift, a practice coming under scrutiny as part of a nationwide review of air traffic control staffing at America's airports.
TIA is one of several around the country that have a single staffer on duty overnight, a practice thrust into the spotlight this week when a lone air traffic controller on duty at Ronald Reagan Washington National Airport reportedly fell asleep on the job.
Two Washington-bound airliners touched down safely by staying in radar contact with a regional facility that watched over the jets as they landed.
The Reagan National controller was working his fourth overnight shift in a row and was suspended from operational duties while a probe is in progress, officials said.
In the aftermath, Federal Transportation Secretary Ray LaHood assigned two controllers to staff the overnight shift at Reagan National and ordered the Federal Aviation Administration "to study staffing levels at other airports around the country," a news release said.
The National Air Traffic Controllers Association told the Associated Press that Tucson is among several airports staffed by one controller overnight.
TIA is one of four airports in Arizona that holds the designation of "international airport." By federal statute, the designation means flights coming from the south must stop at one of these airports for customs clearance. It also means the airports are required to be available 24 hours a day for international flights, according to U.S. Customs and Border Protection.
Sky Harbor Airport in Phoenix holds international "landing rights" and can refuse an international flight if it's landing after hours or at an inconvenient time. Arizona's international airports - Tucson, Yuma, Nogales and Douglas - may not refuse an international flight.
The Tucson Airport Authority, which runs TIA, could not be reached for comment Friday and an official for the FAA would not comment for this story, citing the open investigation.
The national air traffic controllers union maintains that having a single person on duty overnight is inherently risky.
"One-person shifts are unsafe. Period," said Paul Rinaldi, president of the National Air Traffic Controllers Association.
FAA Administrator Randy Babbitt said he was "outraged" by what occurred at Washington National.
"As a former airline pilot, I am personally outraged that this controller did not meet his responsibility to help land (the) two planes," Babbitt said. "I am determined to get to the bottom of this situation for the safety of the traveling public."
The Associated Press contributed to this story. Contact reporter Carol Ann Alaimo at firstname.lastname@example.org or at 573-4138.