WASHINGTON — The head of air traffic control in the United States resigned on Thursday after an embarrassing spate of cases in which controllers were found napping on the job.

The resignation of Hank Krakowski was accepted by Federal Aviation Administration (FAA) chief Randy Babbitt, who promised a major shake-up of the system to win back public trust in its safety.

"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 in a statement.

"This conduct must stop immediately. I am committed to maintaining the highest level of public confidence and that begins with strong leadership."

Babbitt said FAA chief counsel Dave Grizzle would assume the job temporarily while the search for a permanent director of Air Traffic Organization was carried out.

Last month two jets carrying a total of 165 people were forced to land without help at Reagan National Airport, just a few miles from the White House, because the lone controller on the night shift had fallen asleep.

The FAA has revealed that another air traffic controller at a major airport in Seattle has fallen asleep several times, most recently during a morning shift on Monday.

What appeared to be the final straw came on Wednesday when a controller at Reno-Tahoe International Airport in Nevada fell asleep on the job, forcing a medical plane carrying an ill patient to land unaided.

The FAA has also suspended two workers for a March 29 incident in Lubbock, Texas, in which controllers failed to appropriately hand off control of a departing aircraft to a nearby center at Fort Worth.

"I am totally outraged by these incidents," US Transportation Secretary Ray LaHood said in a recent statement. "The American public trusts us to run a safe system."

After the incident at Reagan National, LaHood called on Babbitt to review staffing levels at airports across the country and ordered two controllers to be placed on the night shift at the busy Washington airport.

"It is not acceptable to have just one controller in the tower managing air traffic in this critical air space," he said.

An FAA report in February showed an alarming jump between 2007 and 2010 in air traffic errors from 1,040 to 1,887 -- a rise of 81 percent.

Investigators are currently probing a collision on Monday night between an Air France Airbus A380 and a smaller Delta-Comair commuter aircraft as they taxied on the tarmac of John F. Kennedy International Airport in New York.

Footage aired on NBC New York and available on YouTube at shows the wing of the Air France jet clipping the smaller aircraft and spinning it almost 90 degrees.

A total of 586 passengers and crew were on board the two aircraft when the incident occurred, but no injuries were reported.