After several incidents involving air traffic controllers caught sleeping on the job, federal authorities announced that a second air traffic controller will be added to night shifts at 27 sites around the nation.

As the Associated Press reports, the latest case of sleeping on duty came early Wednesday morning in Reno, Nev., when a controller dozed while a medical plane landed on his runway. It was the fourth such incident this year.

“I am totally outraged by these incidents. This is absolutely unacceptable,” Transportation Secretary Ray LaHood said in a statement. “The American public trusts us to run a safe system. Safety is our No. 1 priority and I am committed to working 24/7 until these problems are corrected.”

Previous episodes of sleeping controllers –and, as a consequence, control towers failing to guide approaching planes– occurred in Knoxville, Tenn., Washington, D.C., and Seattle. In another example of a lapse, two controllers were suspended in Lubbock, Tex., after they twice failed to take a “handoff,” which means that they did not properly assume responsibility for a flight as it approached their airport.

As with all the planes that have been forced to land while controllers dozed, the small plane touched down in Reno without incident. The Reno controller was out of touch for 16 minutes.

The National Air Traffic Controllers Association has long advocated against grueling hours and working solo on night shifts.

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