The backlog of travellers at Heathrow is beginning to ease, with around two thirds of flights operating today.
The airport is warning passengers not to travel to the airport unless their flight has been confirmed as operating by their airline.
Passengers on flights that have not been confirmed will not be allowed to enter the terminals.
Like most airlines, British Airways today is focused on returning to normal schedules, but cancellations and delays are still likely as planes and staff are moved to where they should be.
Most airports are able to operate near normal services, but knock-on delays continue due to adverse weather elsewhere.
Southampton, Edinburgh, London City, Gatwick, Birmingham and Manchester airports are open, but some disruption to flights may occur.