British Airways has asked Heathrow to deploy security personnel to prevent passengers from entering their homes in Terminal 5. Previously, the airline was forced to cancel all short-haul flights in Europe on Saturday.
On Friday night, the airline suffered a massive IT glitch that shut down critical operating systems for more than five hours before the airline decided to cancel more than 200 flights early.
A British Airways spokesperson denied reports that the Russian-backed cyberattack was responsible for the flight disruption and said the backup system had been activated. Witnesses, however, said the airline was "on paper" after staff had to move to manual, labor-intensive processes.
Heathrow airport said British Airways had asked it to restrict access to airport terminals because thousands of passengers were trapped and had nowhere to go. As a result, there are concerns that Terminal 5 could be dangerously crowded.
British Airways warns passengers to stay away from the airport as there are no staff available to help rebook tickets. Passengers were urged to use the airline's faulty website to explore options for rebooking.
A spokesman also suggested that affected passengers could request travel vouchers in the future, but consumer rights activists warned that using vouchers would prevent BA from meeting its care duty.
With British Airways' entire short-haul flights cancelled, Heathrow also warned that luggage was starting to pile up. Last week, a winter snowstorm at Heathrow caused traffic chaos and forced thousands of passengers to wait days for delayed luggage.