A second day of fog across much of the country threatens to compound disruption to flights caused by a general strike in France.
Many flights were delayed or re-routed yesterday due to the bad weather conditions
More than 120 inbound and outbound flights were cancelled at Heathrow with others facing delays.
London City Airport and Stansted also reported disruption while Newcastle airport was forced to cancel flights because of the bad weather.
Passengers face more cancellations and delays today after the Met Office issued a 17-hour severe weather alert in the South, Midlands and north of England because of the fog.
Eleven early morning departures from London City have been cancelled together with 15 inbound services, including flights to and from Scotland.
EasyJet warned of disruption to flights across the south of England due to fog this morning.
Flights departing from Southend to Belfast and Amsterdam were operating to and from Stansted with coach transfers laid on between the two Essex airports.
“Due to the nature of fog, some of the limitations imposed by air traffic control are flexible and so we would encourage you to present yourself at the gate at the normal time,” the airline said in a posting on its website.
Bristol airport warned this morning of air traffic control delays caused by striking French civil service workers. Passengers were advised to check-in on time and check airline websites for updated flight information.
Southampton airport also warned of possible delays and flight cancellations this morning.
A Heathrow spokesman said: “There are delays and cancellations due to fog and industrial action in France.”