Tens of thousands of travelers whose holiday weekend plans included a trans-Atlantic hop or a jaunt around Europe probably met with some unpleasantness this weekend, as an IT problem led to British Airways cancelling hundreds of flights and leaving more than 75,000 passengers in the lurch.

The problem struck on Saturday, when a power surge apparently led to a “catastrophic” systems failure that affected BA’s primary and backup systems.

In a video statement posted Saturday, British Airwys CEO Alex Cruz said the airline was experiencing a “major IT system failure” that caused “very severe disruption” to the airline’s operations worldwide.

The cause was a power failure, Cruz said, adding that BA had “no evidence of a cyber attack.”

All check-in and operations systems were affected, and the airline cancelled all flights from London’s Heathrow and Gatwick airports on May 27. Worse: all of the call centers were also affected by the IT problem, and so tens of thousands of confused and frustrated customers couldn’t get flight statuses or rebook their cancelled flights.

Cruz directed customers to Twitter for updates instead, adding several apologies for the “huge inconvenience.”

Many of the airline’s IT systems were restored by Sunday, but not all. Travelers were still stranded when Cruz issued another statement.

“I know this has been a horrible time for customers,” Cruz said. “Some of you have missed holidays. Some of you have been stranded on aircraft and some of you have been separated from your bags. Many of you have been stuck in long queues while you’ve waited for information.”

Cruz begged travelers not to show up too early, and to double-check first that their flight was actually going to happen, as Heathrow was simply too crowded with people to accommodate more.

Airline operations continued to recover on Monday, and today so far FlightAware reports that only one British Airways flight has been cancelled, though more than a hundred are already delayed.

You may be feeling a vague sense of deja vu, but it’s not you: this really is the second time in less than a year a big IT problem has affected British Airways worldwide. The airline suffered a massive worldwide glitch in Sept. 2016 that took out its check-in systems globally and led to massive delays everywhere it flies, including U.S. airports. And that followed a smaller IT failure in July, 2016, that also affected check-in systems.

But airline computer systems failures are far from unique to British Airways. United, Delta, Southwest, and the TSA itself have all had major systems problems — some, more than once — within the last year that delayed or stranded tens of thousands of passengers.

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