As noted by Reuters, any U.S. or other passengers hoping to fly out of London Heathrow or Gatwick airport with British Airways will experience endless delays on Saturday, due to a major IT system failure. The airline has canceled all Flights leaving prior to 18:00 local time.

According to a statement from British Airways, a “major IT system failure” has caused severe disruption to their worldwide flight operations. The airline apologized for the delays, stating that they are working to resolve the problem. Reportedly London Heathrow Airport is also working closely with with the airline in an attempt to resolve the issue.

BBC’s business correspondent, Joe Lynam, has been told there is no evidence of a cyber attack relating to the system failure.

British Airways warns passengers to stay away from the airports

The airline has warned passengers with flights leaving before 18:00 local time on Saturday to stay away from both Heathrow and Gatwick airports as both are currently “extremely congested” with waiting passengers. Anyone booked on flights up until that time has the option of either rescheduling their flight or receiving a refund.

However, many passengers who have tried to reschedule their flights have come up short, as the airline cannot access their computer system to find which flights are available.

Numerous problems experienced due to British Airways IT system outage

The IT system outage is causing numerous problems, including the fact that certain areas of the British Airways website are currently unavailable, with many passengers finding they could not check in using the mobile app.

Gates are being blocked by planes that are unable to take off, resulting in incoming flights being unable to land or park at the airports.

Other cities experiencing delays with British Airways flights

The problems experienced at Heathrow and Gatwick are causing a ripple effect, with major delays in other European cities, including Malaga, Milan, Prague, Rome, and Stockholm.

Delays are also affecting other U.K. cities, leading to travelers taking to Twitter to complain.

As noted by Reuters, one Twitter user was supposed to be flying to Las Vegas today but is currently stuck on the tarmac in Leeds airport, unable to catch his connecting flight.

According to one Twitter user, Martin Patience, British Airways staff in Heathrow have had to resort to the use of old school white boards, rather than computer equipment.

Many Twitter users quipped that the airline should try turning the IT system off and on again.

Another passenger mentioned that the luggage conveyors are also down at Heathrow.

However, some Twitter users managed to keep a sense of humor when fast food started running low at the airport, by referring to the current threat levels in the U.K.