Delta Airlines grounded its domestic flights Sunday evening, citing what what it called "technical issues."
Detroit Metro Airport officials later said the Delta reservation system was down, delaying or canceling all of the airline's flights.
UPDATE: Delta operations returning to normal after systems outage
The airline said not all delays or cancellations are being reflected on Delta systems, including Delta.com, the Fly Delta app, airport information screens or through reservation agents
Delta officials said via the air carrier's Twitter page its information technology department was working to rectify the situation.
"The IT department is working to rectify the situation as soon as possible," the tweet read.
Officials said international flights were exempt from the airline's action.
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