Delta Air Lines says its entire worldwide network of computers has been shut down, causing all its flights to be delayed.

“Our systems are down everywhere. Hopefully it won't be much longer,” the airline said in a tweet on Monday.

As a result of the outage, Delta flights have been hit with long delays at London's Heathrow Airport, Los Angeles International, Seattle-Tacoma International Airport, San Francisco International and Rome's Fiumicino.

Delta passengers across the world took to social networking websites to complain about the situation.

“We're currently experiencing system issues and working to resolve it asap,” the airline responded on its Twitter page.

The company released a statement later in the day, saying it was looking for the cause of the system failure.

“Delta experienced a computer outage that has impacted flights scheduled for this morning. Flights awaiting departure are currently delayed. Flights enroute are operating normally. Delta is advising travelers to check the status of their flights this morning while the issue is being addressed,” the statement read.