More than 500 flights at O’Hare International Airport and Midway Airport were delayed this morning because of a computer outage at the Federal Aviation Administration that brought flights across the country to a standstill. Another 89 flights at the two airports were canceled, according to the flight tracking website FlightAware.

The FAA lifted its ground stop just before 8 am Central Wednesday morning, but residual delays and cancellations were expected to continue as airlines worked to resume flights. United and Southwest were encouraging passengers to check the status of their flights.

Marty Halston said his Southwest flight from Midway to Fort Lauderdale was delayed about two hours and forty minutes Wednesday morning. The delay was unfortunate, but waiting passengers were orderly and the staff was helpful, even as the airport got crowded, he said.

“You got three groups of people at every gate, because the people that are coming for the 9:30 flights and the people that are here for the 6 a.m. flight are all on top of each other,” he said.

He only flies a few times a year, and chalked the delay up to a bad break, he said.

“What are you going to do?” Halston said as he prepared to board his flight and start a vacation with friends. “You can’t fly, you can’t fly.”

The FAA said it was working on restoring its Notice to Air Missions System.

“We are performing final validation checks and reloading the system now,” the FAA said. “Operations across the National Airspace System are affected.”

The agency said that some functions are beginning to come back on line, but that “National Airspace System operations remain limited.”

The Associated Press contributed.