The airline said the problem, which impacted its operation at Heathrow Terminal 5, has now been resolved. A Heathrow spokesperson advised customers to check their flight status with British Airways before travelling to the airport.
"We experienced a technical issue for a short time this afternoon," BA said in a statement. "This has now been resolved and we're resuming flight operations. We've apologised to those customers who have been inconvenienced."
The airline, owned by IAG ICAG.L, was hit by a major computer system failure in 2017 that stranded 75,000 passengers over a holiday weekend, sparking a public relations disaster and pledges from the carrier that it would do better in the future.
It was also hit by a "significant technical issue" in February that led to a number of cancellations and disruption across its network which took many hours to resolve.
The online departure board at Heathrow on Wednesday afternoon showed flights delayed, with a few cancelled.
"Hey @British_Airways, our captain has tried to call, email to let you know your IT systems are down so your whole fleet is grounded. Just tweeting you in case you hadn't heard," a Christian Hernandez said on Twitter.