CHICAGO - Hundreds of flights were delayed and canceled in Chicago on Wednesday morning after the Federal Aviation Administration reported a system failure nationwide, temporarily grounding all domestic flight departures.
Nearly 100 flights at O'Hare have been canceled while 42 have been canceled so far at Midway.
During mid-morning, Midway was reporting average delays of two and a half hours.
A statement from the FAA noted an issue with NOTAM (Notice to Air Missions), a system that sends out critical information to pilots and other flight operations personnel about potential hazards along a route. The alerts span from mundane information about construction at airports to urgent flight restrictions or broken equipment.
All aircraft are required to route through the system, including commercial and military flights.
As a result of the issue, the FAA said it ordered all airlines to pause all domestic departures until 9 a.m. Eastern Time "to allow the agency to validate the integrity of flight and safety information."
The FAA sent out an update just after 7 a.m. saying departures were resuming at Newark Liberty and Atlanta Hartsfield-Jackson airports due to air traffic congestion in those areas. The agency still expects departures to resume at other airports later this morning.
United Airlines told FOX Television Stations in its own statement that it had "temporarily delayed all domestic flights and will issue an update when we learn more from the FAA."
The ground stop was lifted just before 9 a.m. ET.
However, delays and cancelations continue to snowball.
More than 3,700 flights were delayed and more than 640 were canceled nationwide.
Fox News contributed to this report.