More Than 500 O'Hare, Midway Flights Delayed By FAA Computer Outage

CHICAGO — More than 500 flights at O’Hare International and Midway airports were delayed and another 89 were canceled on Wednesday morning after a computer outage at the Federal Aviation Administration grounded U.S. domestic flights around the country.

Domestic U.S. flights are gradually resuming, and the ground stop was lifted just before 8 a.m. after the FAA ordered airlines to pause all domestic departures early Wednesday — resulting in a ripple effect of thousands of delays and hundreds of cancellations — following an outage to its Notice to Air Missions system.

At O’Hare, travelers are seeing delays of just under 90 minutes, according to the flight-tracking website, FlightAware, while at Midway, delays are approaching nearly two hours. The delays and cancellations come just weeks after thousands of holiday travelers were stranded at the city’s two airports due to difficulties experienced by Southwest Airlines.

On Wednesday, United — the major carrier at O’Hare — encouraged travelers to check the status of their flights. In a tweet, the airline said that customers impacted by Wednesday morning’s disruption could get travel waivers “to allow you the freedom and flexibility to change your travel plans.”

President Joe Biden was briefed on the outage Wednesday morning. The White House said initially there is no evidence of a cyberattack at this point and Biden told reporters that he’s directed the Department of Transportation to investigate the cause of the disruption. The pause was ordered around 7:20 a.m. Eastern time.

The Notice to Air Missions system provides safety information to flight crews. The FAA said it ordered the pause to allow it time to validate the integrity of flight and safety information.

The FAA lifted the ground stop as of 8:50 a.m. Secretary of Transportation Pete Buttigieg said he has directed an after-action process to learn the root cause of the outage and recommend next steps.

Flights that were in the sky could land safely while the ground stop was in place, the FAA said.

"A Notice to Air Missions alerts pilots about closed runways, equipment outages, and other potential hazards along a flight route or at a location that could affect the flight," the agency explained.

More than 21,000 flights were scheduled to take off in the U.S. (Wednesday), mostly domestic trips, and about 1,840 international flights were expected to fly to the U.S., according to aviation data firm Cirium.

As of 9:05 a.m. Central time., 899 flights within, into, or out of the United States have been canceled, while 5,417 were delayed, according to flight-tracking website FlightAware.

Some airlines had begun grounding flights even before the FAA ordered the pause.

In a statement, American Airlines said it was closely monitoring the situation and working with the FAA to minimize customer disruptions.

The Associated Press contributed to this report.