British Airways flights out of Heathrow’s Terminal 5 were affected by a “technical issue” on Wednesday.
The airline apologised to customers who were inconvenienced by the problem, saying it had affected its operation for “a short time”.
In a tweet it later confirmed the issue had been resolved and it was working to help passengers whose journeys had been disrupted.
The issue is the latest to beset the airline in recent months.
In late February, the airline was forced to cancel all short-haul flights from Heathrow for several hours due to a hardware problem.
It led to hundreds queuing outside Heathrow’s Terminal 5 with staff only letting passengers into the building an hour before their flight, due to the backlog.
The airline apologised at the time for the issue.
In a statement on Wednesday, a British Airways spokesman said: “We experienced a technical issue for a short time this afternoon which affected our operation at Heathrow Terminal 5.
“This has now been resolved and we’re resuming flight operations.
“We’ve apologised to those customers who have been inconvenienced.”
According to British Airways’ website, dozens of flights due to leave Heathrow Terminal 5 between 1pm and 6pm on Wednesday were cancelled or departed late.
The site also shows others departed on time or early.
Rory Boland, Editor of Which? Travel, said: “Passengers will rightly be very angry about this disruption just weeks after the last time British Airways experienced technical issues.
“In events such as these, airlines should be offering the option of a refund or to reroute passengers on any reasonable route as quickly as possible, using other airlines where necessary.
“BA must also give clear information to customers about the situation and their entitlement to assistance and compensation.”
In a tweet, Heathrow Airport said: “A technical issue which affected British Airways this afternoon has now been resolved.
“We’re working with our airport partners to assist passengers whose journeys have been disrupted and have deployed additional resource in our terminals.
“Passengers are still advised to check their flight status with British Airways before travelling to the airport due to a number of resulting cancellations.
“We apologise for any inconvenience caused.”