Heathrow Airport said it is "operating as normal" after suffering an IT glitch on Sunday that saw passengers reading their flight times on whiteboards.
More than 200 flights were cancelled due to the issue, which was further exacerbated by Storm Dennis.
Digital notice boards stopped working, causing passengers to miss flights, most of which were already delayed by the bad weather.
Although the airport has said that its back up and running, more delays are expected for Monday as airlines deal with the backlog.
"Following yesterday's technical issue Heathrow's systems are stable and the airport is operating as normal," a spokesperson said. "We apologise for the inconvenience this caused our passengers. Our teams continue to closely monitor our systems and will be on hand across our terminals to provide assistance to passengers."
British Airways, which saw 20 flights cancelled on Sunday due to the problems, suggested there would be further consequences for Monday's travellers.
"The technical issue with Heathrow Airport's systems has now been resolved, but after ten hours of disruption across all terminals, we do expect to see a knock-on effect to today's short-haul schedule," the airline said in a statement to IT Pro.
BA suffered similar problems in August 2019 that saw around 300 flights either cancelled or delayed at Heathrow, Gatwick and City airports. After Sunday's issues, it said it will offer customers a flexible booking policy to compensate and will deploy extra staff to help.
Other airlines are also looking to get things back to normal, though many are still having difficulties due to the strong conditions. A clip of an Eithad plane landing in the extreme weather conditions has gone viral, with the pilots praised for their composure.
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