Airports in the Washington and New York City areas were hit hard.
At Ronald Reagan Washington National Airport
, thousands of travelers wandered with strained expressions, looking for bags from the endless list of canceled flights. Other passengers were trying to rebook flights only to find they cannot get one for days.
Many people waited three hours just for their luggage to come back, and that followed waits of as long as five hours before they learned their flights weren't taking off.
"It was a horrible travel day, but I think there was such relief that it wasn't terror," said Lisa Picard, who was trying to go from Reagan to Orlando with her husband and two children. "There were a lot of nice people at (the airport) and people were actually trying to help each other."
The Picards were particularly unlucky. Their flight was about to push back -- they even heard the safety talk -- when they were told to sit and wait. After 90 minutes it looked like they were headed for another takeoff, but that was scrapped, too. After three hours, the flight was canceled.
The next available flight was Monday, so they loaded up the car and are driving the 850 miles to Orlando instead.
Just after 4 p.m. ET, the FAA tweeted that an automation system that experienced problems was back in service.
"The agency is working w/airlines to return to normal operations," it tweeted.
The FAA never said what the problem was with the computer system that processes flight plans at the Washington Air Route Traffic Control Center in Leesburg, Virginia. The issue forced the FAA to temporarily halt departures for all planes at the D.C.-area's three major airports, the agency said.
The repercussions, though, were felt nationwide.
American Airlines spokeswoman Laura Nedbal said the carrier called off 245 flights, 66 of which were at Reagan National.
Passengers at Reagan reported departure delays of several hours through late afternoon. According to the flight-tracking website flightaware.com
, 25% of scheduled departures from Reagan were canceled.
The same percentage of flights were canceled at Baltimore/Washington International Airport
Even a significant number of flights at Raleigh-Durham International
, Richmond International
and Myrtle Beach International
Airports were delayed, though not all delays were due to the FAA computer issues.
Flight Aware said there were more than 3,400 delays and 640 cancellations involving flights originating in or flying to the United States on Saturday.
There were plenty of problems for people trying to get to D.C. too.
Passenger Blake Jones from Colorado said he was missing meetings while stuck on a plane that had been diverted to Dulles International Airport
. The flight was 30 minutes from landing at Reagan National when the pilot told passengers they were going to land elsewhere and wait until they could continue to their original destination.
"I didn't know I was claustrophobic until now," Blake, laughing at his predicament, told CNN after two hours -- and counting -- on the Dulles tarmac. He said the flight crew distributed water after about 90 minutes and passengers were still in good spirits.
"I'm just disappointed because I paid for a ticket to get to Reagan in a timely manner," he said. "I had plans for the rest of the day, meetings scheduled that I had to cancel."
He was flying Frontier, as was Ben Rosenfield. He was on his way from Charlotte, North Carolina, to Philadelphia to attend a wedding.
His flight was delayed two hours after all the passengers boarded. He didn't make the ceremony but had a chance to make the reception, he said.
"In a nutshell, I'd say I feel frustrated, annoyed, and angry," he said.
The problem also affected planes that were in the sky at the time of the computer problem, with "high-altitude traffic" diverted around the center's airspace, FAA spokeswoman Kathleen Bergen said.
Earlier Saturday, a map on flight-tracking website FlightRadar24.com
seemed to illustrate the effect: Very few fights were shown over large parts of North Carolina, Virginia, Maryland, and Delaware.
More planes were in the airspace by 1:30 p.m., with planes finally departing Washington-area airports. But planes taking off from the Washington airspace were being kept at an elevation of 10,000 feet or lower, images from FlightRadar24.com showed.
Major airlines acknowledged the East Coast delays.
"We have to make last-minute adjustments to flight plans," Delta Air Lines spokesman Morgan Durrant said. "Flights in and out of the three major D.C.-area airports may be delayed."
"There is an issue with air traffic control impacting all airlines' east coast flights. Please plan accordingly," American Airlines said on Twitter.