LONDON (AP) — Delta Airlines has grounded flights scheduled to leave Monday after experiencing unspecified systems issues.

Confirmation of Monday’s troubles came in an official account that responds to customers via Twitter. The airline declined to immediately comment by phone and it was unclear whether all its flights were affected.

“Delta has experienced a computer outage that has affected flights scheduled for this morning,” the company tweeted to customers affected by delays. “Flights awaiting departure are currently delayed. Flights enroute are operating normally. We appreciate your patience.”

The company said its IT systems were down everywhere and “hopefully it won’t be much longer.”

Several applications were affected, including the company’s website.

Passengers whose Delta flights are cancelled or significantly delayed Monday will be able to get a travel waiver for another flight. Visit Delta’s website for more information.