A second air traffic controller was recently found to have fallen alseep while on the job, NBC News reports.
The incident allegedly took place Feb. 19 during the controller's midnight shift at McGhee Tyson Airport in Knoxville, Tenn.
The Federal Aviation Administration is taking steps to fire the air traffic controller.
The incident came to light during a congressional hearing Wednesday. FAA Administrator Randy Babbitt was asked about a March 23 incident in which two airplanes landed without assistance at Reagan National Airport in Washington, D.C., after the lone controller on duty acknowledged falling asleep while on duty. He had been working his fourth 10 p.m. to 6 a.m. shift in a row.
The controller was suspended, prompting the FAA to review overnight staffing at selected airports around the country.
During Wednesday's hearing, CNN reports that Rep. Tom Latham, R-Iowa, asked Babbitt: "Have there been other incidents of the same thing?"
"Yes sir, we actually, I'm disappointed to say, in our investigation, we did find another incident," Babbitt responded. "And it was, unfortunately, willful."
The McGhee Tyson Airport is considered an "up-down facility," meaning the airport control tower and the radar room are staffed on separate floors. The controller in the tower reportedly helped seven planes land during a five-hour period while the controller on duty in the radar room reportedly went to sleep.
The FAA has suspended two air traffic controllers in the past month. In the second incident, a controller was disciplined after asking the pilots of a Southwest Airlines flight for help determining the status of a private plane in central Florida that had been out of radio contact for over an hour, according to the FAA. An investigation shows that the planes came too close together, a violation of FAA regulations.