British Airways told Express.co.uk: “We are extremely sorry that due to the continuing technical issues we are facing we have regrettably had to cancel a significant number of short-haul flights from Heathrow today.
“Customers due to travel later today should check their flight status on ba.com before coming to the airport as we anticipate further disruption during the day.
“Our long-haul services at Heathrow and all flights at Gatwick and London City Airport are due to operate as planned, but customers may experience some delays.
“Our website ba.com is working and customers can check-in online and at the airport. We are offering customers on cancelled services the option of a refund or to rebook onto another service. We will be contacting customers proactively.
“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.”