The Federal Aviation Administration launched a review of the nation's air traffic system after a top agency official resigned Thursday because controllers fell asleep on the job.
The resignation of Henry Krakowski, who was responsible for operations, planning and maintenance of the air traffic control system, comes after a series of high-profile embarrassments in several states and Washington, D.C., where controllers have fallen asleep while working overnight shifts.
At least five controllers have been suspended in recent months, and the agency has moved to increase the late staffing from one person to two.
"We are conducting a top-to-bottom review of the way we operate our air traffic control system," said FAA Administrator Randy Babbitt. "We are all responsible and accountable for safety — from senior FAA leadership to the controller in the tower."
The FAA's chief counsel, David Grizzle, will temporarily take over the Air Traffic Organization, which employs 38,000 of the FAA's 48,000 workers.
Babbitt tried to reassure air travelers.
"Over the last few weeks we have seen examples of unprofessional conduct on the part of a few individuals that have rightly caused the traveling public to question our ability to ensure their safety," he said. "This conduct must stop immediately. I am committed to maintaining the highest level of public confidence, and that begins with strong leadership."
After a controller in the tower dozed off last month, two jets landed without clearance at Reagan National Airport, which serves the Washington, D.C., area. A medical flight carrying an ill patient was forced to land on its own this week at Reno-Tahoe International Airport after a controller there reportedly was asleep.
Other incidents have been reported in the states of Washington, Texas and Tennessee.
The cases sparked complaints that the staffing at control towers was inadequate. On Wednesday, the FAA announced that it would add controllers at 27 towers around the country, including Bob Hope Airport in Burbank and Los Angeles/Ontario International Airport in San Bernardino County.
The National Transportation Safety Board has also launched an investigation, and the House Transportation Committee has said it would conduct a review of the sleeping incidents.