UPDATE: Delta tweeted shortly after 10 p.m. MT, stating that the ground stop has been lifted and systems are returning to normal.
The airline states about 150 flights have been canceled Sunday night, and they added that not all delays and cancellations are reflected properly in Delta systems.
A travel waiver has been issued for January 29 and 30 with a rebooking deadline of February 3.
Previous story continues below:
By Robert Mclean
NEW YORK (CNNMoney) — Delta was hit by a crippling computer outage on Sunday night that disrupted flights across the United States.
It’s the second time in less than six months that the U.S. carrier has suffered a major IT problem resulting in cancellations, delays and angry passengers.
The FAA announced a nationwide ground stop late Sunday on all domestic Delta flights. The measure remained in place for at least two and half hours it was lifted.
“Delta teams are expeditiously working to fix a systems outage that has resulted in departure delays and cancellations,” the company said in a statement.
It wasn’t immediately clear how many flights were affected in total and to what extent the problems might spill into Monday.
Upset travelers took to Twitter to vent about the delays and confusion.
“@Delta I’m here in Atlanta will they let us know when things start working again?” wrote Twitter user @Indydog63.
The airline’s website and mobile apps also went down, adding to customers’ frustrations.
Delta said that flights in the air weren’t affected by the outage but that some passengers were experiencing delays after landing.
It apologized to customers “for the inconvenience.”
The FAA said in its advisories that international flights weren’t affected by the ground stop. But some people said on Twitter that Delta flights to foreign destinations were disrupted.
“Despite claim that international flights are not impacted, my @delta flight to England is indeed still impacted,” tweeted @accountingninja.
Delta didn’t immediately respond to a request for further information.
The problems come about a week after United Airlines temporarily grounded domestic mainline flights due to an IT issue.
A previous Delta outage caused travel chaos around the globe.
In August, the airline lost power at its operations center in Atlanta setting off a system failure that resulted in around 2,000 flight cancellations over several days.
After that fiasco, Delta agreed to give affected customers refunds and vouchers for future travel.
— Tony Marco and Chris Isidore contributed to this article.
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