Flights resumed on Tuesday at airports on the US East Coast after a powerful earthquake grounded planes and delayed tens of thousands of passengers during the mid-afternoon travel rush.
Airline operations were halted in Washington, New York and Philadelphia for more than 90 minutes to allow runway, control tower and terminal inspections, federal and local transportation officials said.
One terminal at Washington's Ronald Reagan National Airport was evacuated as firefighters investigated a potential gas leak, but no leak was found. The air traffic control tower there was evacuated briefly.
US Airways, which has heavy schedules in Philadelphia and Washington, anticipated many delays.
Delta Air Lines said it expected to cancel a dozen flights at New York's John F Kennedy airport and a dozen at Reagan National.
American Airlines said it had diverted four flights.