The official in charge of air traffic controllers for the Federal Aviation Administration resigned Thursday after a series of episodes in which controllers across the country slept as airplanes landed.

Henry P. Krakowski, the chief operating officer of the agency’s Air Traffic Organization, tendered his resignation one day after the agency changed its policy permitting a single air traffic controller at each of 27 airports across the country overnight. Each of those airports will now have at least two controllers at night.

In recent weeks, several controllers — including one at Ronald Reagan Washington National Airport — were found to have been asleep while on duty as pilots seeking to land tried to contact the control tower.

The episodes have prompted angry responses from lawmakers and scathing criticism from the federal officials charged with overseeing air safety.