WASHINGTON---At least four more U.S. air-traffic controllers are caught nodding off on the job at three separate airports across the nation, the government said Wednesday. The controller working alone in the tower fell asleep and was out of communication for 16 minutes while a medical flight carrying a patient was trying to land at about 2 A.M. Wednesday at Reno-Tahoe International Airport in Nevada, the Federal Aviation Administration (FAA) said in a statement.  The FAA announced that it is also investigating a controller who fell asleep Monday at Boeing King County International Airport in Seattle and two controllers who were unresponsive at Preston Smith International Airport in Lubbock, Texas, on March 29.The agency had earlier revealed that an air-traffic supervisor fell asleep March 23 at Ronald Reagan Washington National Airport and a controller slept for five hours at McGhee Tyson Airport in Knoxville, Tennessee on Feb.19. "I am sick of this," Senate Commerce, Science and Transportation Chairman Jay Rockefeller, a West Virginia Democrat, said in a statement. "We can't have an aviation system where some of the people responsible for safety are asleep at the switch."  As the incidents pile up, sleep experts say it demonstrates that the agency faces a systemic issue with the thousands of people expected to work through the night in safety-critical jobs. Scientific research shows that workers on midnight shifts make more errors because it is so difficult for the body to adapt to sleeping during the day, they say. ks5u The agency will add an extra controller at the 27 towers staffed with one worker on the midnight shift, the FAA statement said. Agency chief Randy Babbitt and the controllers' union president, Paul Rinaldi, will visit facilities around the country next week to reinforce the need for "the highest professional standards," according to the FAA.  Doug Church, a spokesman for Rinaldi of the National Air Traffic Controllers Association, didn't immediately return a telephone call for comment.  Representative John Mica, the Florida Republican who chairs the House transportation committee, criticized the decision to add controllers. "Only in the federal government would you  _ , averaging $161,000 per year in salary and benefits, that aren't doing their job," Mica said in a statement. Mica has pushed legislation  that would allow as many as 90 smaller airports to switch from federal to private controllers.  "People have known these problems with fatigue have existed for years," said John Goglia, a Boston-based aviation safety consultant. "They're now showing up. The FAA is admitting they exist. Now the FAA needs to work on it." Babbitt said April 6 a controller was in the process of being fired for deliberately sleeping on the job at the McGhee Tyson Airport in Knoxville, Tennessee, on February 19.  The four controllers in Nevada, Seattle and Texas have been suspended pending investigations, the FAA said. We can infer from the passage that   _  .
The controllers were working alone while they were on duty The incidents are rooted in fatigue problems and those on midnight shifts need an extra nap In the U.S. , thousands of people expect to work through the night in safety-critical jobs The agency has added an extra controller at the 27 towers