British Airways has cancelled all mainline domestic flights to and from Heathrow airport for the rest of the day because of severe fog. Flights between Heathrow and mainland Europe are also being severely disrupted by the weather. Gatwick airport has also been affected and inward and outward British Airways flights are facing lengthy delays. The airline has urged customers due to travel on domestic flights to or from Heathrow not to travel to the airport.
Long-haul flights are still going ahead but you can expect severe delays.