According to the BBC, BA said the problem was not a cyber attack but was instead related to a hardware issue.
Long-haul flights continued to operate with minor delays, but all short-haul services were cancelled until midday Saturday (26 February).
Passengers travelling from Gatwick and London City airport also reportedly faced some delays due to the issues.
A BA spokesperson reportedly said: "We are extremely sorry that due to the continuing technical issues we are facing we have regrettably had to cancel all short-haul flights from Heathrow today [Saturday] until midday.
"Our teams have been working hard through the night and will continue to do so to resolve the issue as soon as possible. We advise our customers due to travel today to check ba.com for the latest flight information before coming to the airport.
"We know we have let our customers down and we will do everything we can to make this up to them – but for now our focus is on getting as many customers and flights away as we can."
