Delta Airlines plane (Joe Raedle/Getty Images)

Delta Airlines resumed flying again but passengers should continue to expect delays and cancellations to continue.

"While inquiries are high and wait times are long, our customer service agents are doing everything they can to assist. There may also be some lag time in the display of accurate flight status at, the Fly Delta App and from Delta representatives on the phone and in airport," the airline wrote on its website.

Earlier, Delta grounded all flights starting around 2:30 a.m. on Monday morning after a power outage at its Atlanta computer center brought down the entire system.

"Delta flights are now departing worldwide at a rate of multiple flights per minute and over 160 flights in the air currently. There is still a backlog of hundreds of flights and passengers will continue to experience mass delays and cancellations, but operations are now on track for a recovery,"'s Daniel Baker said in a statement just before 10 a.m. on Monday.

The airline said it is aware that status screens are reading "on time" and said their IT teams are working to resolve the problem quickly.

A waiver has also been granted by the airline for passengers to get refunds and to make a one-time change to their ticket without a fee.

Word of the grounding was first acknowledged in tweets to customers.

"All flights are grounded due to a system outage nationwide" wrote the airline in response to a tweet from a customer.

No further details were offered about the problem.

Customers report long lines at airports around the world.