Dozens of flights into and out of London airports have been disrupted after parts of England woke up to a blanket of heavy fog.
At least six flights were cancelled and more than 85 have been delayed amid poor visibility at Heathrow, Gatwick, Stansted and London City on Friday morning.
The Met Office issued a yellow weather warning for a swathe of the country and said rush-hour bus and train journeys could also be disrupted.
Six short-haul flights from London City airport were cancelled, affecting passengers travelling to destinations including Dusseldorf, Amsterdam and Malaga. A further 10 flights from the airport were delayed, including journeys to Ibiza, Berlin and the Isle of Man.
Forty-one departures at Heathrow, the UK's busiest airport, were delayed by at least 15 minutes between 6am and 9am. A total of 35 departures at Gatwick were delayed over the same period.
Fog forces air traffic controllers to rely more heavily on radar rather than physically looking at the aircraft they are guiding. It means the spacing between planes has to be increased, reducing the rate at which flights can take off and arrive.
Other European airports affected by fog on Friday included Brussels, Amsterdam, Paris Charles de Gaulle and Venice.
The Met Office issued a warning covering parts of the East Midlands, Suffolk, the South East and the South West until 10am, with the fog slowly clearing over the morning.
Friday is set to bring mild temperatures for much of the UK, with highs of 13C in London, 15C in Leeds, 14C in Edinburgh and 16C in Aberystwyth.
Thursday was the warmest February day on record in Scotland, as Aboyne in Aberdeenshire hit a temperature of 18.3C on Thursday afternoon.
It beat the previous high of 17.9C recorded in Aberdeen on 22 February, 1897.
Temperatures are expected to remain mild for the rest of the month.
Met Office chief meteorologist Steve Willington said: “By the weekend we could see temperatures almost 10 degrees higher than what we might normally expect at this time of year, so there will certainly be a spring-like feel in the air across the country.”
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