Heathrow has reduced the number of flights by 10 per cent due to poor visibilty caused by snow and extreme weather conditions.
A spokesman said the reason for this is that when there is low visibility, more space has to be left between aircraft.
Most airport are able to accommodate this, but because Heathrow operates at almost full capacity, there is no room to reschedule the delayed flights.
Cancelling flights in advance introduces space into the schedule and aims to reduce disruption for passengers by:
Allowing airlines to rebook passengers onto un-allocated seats on other flights, significantly reducing the number of passengers that cannot travel that day
Giving passengers clear information about the status of their flight so they can rebook from home or their hotel
Helping to avoid flights being cancelled at short notice, significantly reducing the chances of people staying at terminals overnight.
All passenger are advised to contact their airlines before leaving for the airport today.