Another air traffic controller was found asleep on the job, but unlike the incident at a Washington, D.C., airport last month in which a controller inadvertently dozed off, this was apparently no accident.
The Federal Aviation Administration said a controller in Knoxville, Tenn., deliberately went to sleep on the job during a midnight shift on Feb. 19. Sources told ABC News that the sleeping controller didn't simply nod off -- he made a bed on the floor of the control tower, using couch pillows from the employee break room and a blanket.
The frightening tale once again played out on recordings of radio transmissions obtained exclusively by ABC News from the website liveatc.net.
"Yes sir, we're trying to get a hold of Knoxville approach or Knoxville departure ... and we cannot raise them," said one pilot on approach.
"Poppa Charlie stand by," said another controller at the same airport.
"We got our clearance, but we don't have any radio contact with them," the pilot responded.
The second controller in the tower, working on a different floor, fielded calls from pilots who had heard only radio silence.
The controller who was awake handled seven flights alone, including a Delta Connection arriving from LaGuardia and at least four "Lifeguard" flights. "Lifeguard" flights are planes with an urgent medical mission.
The snoozing controller did respond to one radio call but sounded groggy. The recording was unintelligible.
"Tower, Life Guard 1CW, same as the other guy, nobody home," said one pilot after radio silence.
FAA administrator Randy Babbitt said they are trying to get the sleeping controller fired.
"It was unfortunately willful, and we are in the process of disciplinary proceedings which will terminate this employee," Babbitt said Wednesday at a congressional hearing.
The revelation of this incident comes on the heels of another sleeping controller last month at Washington, D.C.'s Reagan National Airport.
A controller there on his fourth consecutive overnight shift left the radio tower silent after apparently nodding off. Two commercial airliners were forced to land on their own.
That controller, who has not been named, has been suspended pending an FAA investigation.
One veteran air traffic controller contacted by ABC News said the incident at Reagan would not have presented a danger to passengers, because pilots are trained to land without air traffic control, but that it was highly unusual.
"It's a big deal when two aircraft at Washington National Airport are not able to contact the tower," said Dick Marakovitz, a controller for 27 years. "That's a big deal."
ABC News' Matt Hosford, Jim Sciutto and Bradley Blackburn contributed to this report.