FAA lifts ground stop, allowing domestic flights in US to resume after hours of delays and cancellations following system outage

• The FAA lifted its ground stop on US domestic flights Wednesday morning, allowing them to resume.
• The ground stop resulted in hours of delays and cancellations after an FAA technology system, NOTAM, suffered a nationwide outage.

US domestic flights have been allowed by the Federal Aviation Administration to resume after hours of delays and cancellations.

The FAA's Notice to Air Missions system (NOTAM) suffered a nationwide outage on Tuesday night which ran into Wednesday morning, affecting flights across the US.

It said in an updated statement at 8:50 a.m. ET: "Normal air traffic operations are resuming gradually across the US following an overnight outage to the Notice to Air Missions system that provides safety info to flight crews," adding that the ground stop has been lifted. "We continue to look into the cause of the initial problem."

The FAA ordered airlines to temporarily ground all domestic departures until 9 a.m. ET "to allow the agency to validate the integrity of flight and safety information."

It said in an updated statement at 8:15 a.m. ET that it was "making progress" in restoring the system and that departures were resuming at Newark Liberty and Hartsfield-Jackson Atlanta airports "due to air traffic congestion in those areas."

"United has temporarily delayed all domestic flights and will issue an update when we learn more from the FAA," a spokesperson from the airline told Insider. John F. Kennedy Airport and LAX have told passengers to check their flight status with their airline.

Aviation-data company Cirium told Insider that there were close to 20,000 US domestic flights scheduled for Wednesday.

The NOTAM system sends out information on real-time flight hazards and restrictions to commercial airline pilots.

A Delta Air Lines passenger told Insider that the pilot initially said the airline was not impacted "because they are on a system that allows them to reboot and that the outage didn't impact Delta's ability to take off."

"Their understanding was that this was mostly impacting United flight systems and that we made a good choice to book Delta," Thena Robinson Mock said.

However, Mock added that the pilot came back not long after they taxied out and said that the FAA grounded all flights from all airlines. Passengers were asked to deplane and are now "waiting at the gate to find out when we can take off again," she said at the time of the conversation.

Delta said on its Twitter page on Wednesday: "Delta is focused on managing our operation during this morning's FAA ground stop for all carriers. We will provide more updates as soon as we can."