Passengers of British Airways flights have once again seen their journeys delayed due to an IT failure. Check-in systems for the airline went down in UK airports Heathrow, Gatwick and London City, causing flight delays, extended queues and some to miss their planes.

The unidentified issue comes only a few months after a serious IT failure that grounded all of its flights on May 27. That time, the outage was blamed on a power surge in a London BA data center, but questions still remain over why a separate facility was unable to take over.

Déjà vu

Today’s problems occurred early in the morning British Summer Time, and appear to be slowly resolving as of writing (9:45 BST). It is unclear why the check-in systems failed, although the airline has now moved to a manual check-in process while it tries to work out what happened.

BA support staff said on Twitter: “I’m afraid we’re currently experiencing some system issues at the airport this morning. We’re doing all we can to resolve this.”

Travelers took to Twitter to vent their frustration, with Amanda Jayne Porter‏ writing: “British Airways T5 is absolute carnage with systems down!! Very unhappy customers left right and centre. #stillqueuing.”

Steve Blake‏ said: “Missed my 7:15 flight because BA couldn’t print my boarding pass due to IT failure. Didn’t even have baggage to check in.”

And Peter Musumeci added: “Oh no, looks like @British_Airways experiencing IT issues again. Stuck on the runway for an hour now.”

In addition to May’s outage, the company delayed flights last September due to a separate IT outage. But customers of BA can perhaps take solace in the knowledge that their airline of choice is not alone in suffering numerous IT failures.

In January, Delta Air Lines canceled and grounded flights due to a systems outage, just one week after United Airlines did exactly the same thing.