Fog has caused travel disruption across the south of England, as thousands are facing flight cancellations and delays.
Around 100 flights have been cancelled at Heathrow and others have been cancelled at London City Airport.
Visibility at Heathrow and Gatwick Airport was reduced was reduced to 100 metres, The Telegraph reported.
Those travelling have been advised to check their flight's status before leaving home.
A severe weather warning for dense fog has been issued by the Met Office for London, south east England and parts of south west England this morning.
Although the yellow warning for fog is set to end at 10:30am, low winds and freezing temperatures could mean fog continues into the afternoon, a Met Office forecaster said.
Mark Wilson said: "It looks like it will generally improve through the last part of the morning and into the afternoon, but one or two spots will hang on to fog for much of the rest of today."