The US official overseeing air traffic operations resigned on Thursday over a controversy¹ involving disclosures about sleeping air traffic controllers.

美国民用机场空管人员频频被曝在当班时间睡觉引发争议，美国联邦空管局（FAA）的一名高官本周四为此引咎辞职。

Hank Krakowski, who is director of the FAA's Air Traffic Organization, stepped down amid the revelations, the agency said in a statement.

Krakowski's resignation was accepted by FAA Administrator² Randy Babbitt, who said he was conducting a full review of air traffic operations.

"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," Babbitt said in a statement. "This conduct must stop immediately."

US aviation（航空） regulators suspended two air traffic controllers this week for falling asleep on the job, including one who was out of radio contact while a medical flight was trying land.

The latest incident early on Wednesday in Nevada and one on Monday at Boeing Field in Seattle added to concerns about safety prompted by two other controllers found to have slept at work in recent months in Washington, D.C., and Tennessee.

The incidents have raised questions about adequate overnight staffing at air traffic towers. The FAA said in response to Wednesday's incident at the Reno-Tahoe International Airport that it would add controllers at 27 towers.