DENVER — Flights taking off from Denver International Airport (DIA) were stopped for several hours Wednesday morning after a critical system used by U.S. airlines went offline Tuesday night.
The Federal Aviation Administration (FAA), which is responsible for air travel regulations, ordered all domestic departures to be paused until 7 a.m. mountain time Wednesday to "validate the integrity of flight and safety information."
The FAA lifted the ground stop at 7 a.m. mountain time Wednesday.
"Normal air traffic operations are resuming gradually across the U.S. following an overnight outage to the Notice to Air Missions system that provides safety info to flight crews," the FAA said on Twitter. "The ground stop has been lifted. We continue to look into the cause of the initial problem."
More than 650 flights have been delayed at DIA and there have been 67 cancellations as of 1 p.m., according to Flight Aware.
The FAA said its "NOTAM" system went offline shortly after 9 p.m. Tuesday.
The NOTAM system is designed to provide pilots and air traffic controllers with critical information as it develops, including changes in weather or conditions at a certain airport. The information in NOTAM advisories can be hundreds of pages for some flights, containing details about runway closures, bird hazards or low-altitude obstacles in a flight path.
United Airlines said it was temporarily delaying all domestic flights because of the outage.
On the FAA's website for the NOTAM system, a message warns users that recent entries may not appear.
"Due to system processing delays, recently entered NOTAMs may not be displayed," the message reads.
NOTAM messages issued before the outage were still visible Wednesday morning.
More than 1,200 flights were delayed within, into or out of the U.S. Wednesday morning, according to flight tracking website FlightAware. The website did not cite the NOTAM outage as a factor in the unusually high number of delays.
The industry-wide problem comes less than a month after thousands of flights were canceled or delayed after Christmas, when Southwest Airlines faced major delays due to logistical and tech issues during a winter freeze.
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