Services at Heathrow and London City airports are returning to normal after fog forced the cancellation of flights in and out of London for two days.
A total of 120 departures and 104 arrivals have been cancelled at west London's Heathrow since Sunday.
But the fog has lifted and there are no more restrictions at the airport. Passengers are urged to check with airlines before travelling.
At London City, 13 arrivals and 18 departures were cancelled on Monday.
A spokesman for Heathrow, which deals with an average of 1,300 flights a day, said: "The fog has started to clear and there are now no restrictions on flying.
"There are currently no delays to flights but we advise passengers to check with their airlines before travelling."
A City Airport spokeswoman said it was back on schedule.
At Heathrow on Sunday, some airlines had rebooked passengers on other flights, while others had arranged for accommodation.
Some domestic passengers were taken to their destinations by coaches, the airport said.
Philip Dunne, from London, had his flight from Geneva delayed by three hours.
He said: "That I could deal with, but not the huge queues at immigration of over an hour minimum. It's a disgrace."
Delayed passengers complained of "inefficiency" at passport control and the damaging impression they said it created for foreign visitors.
A UK Border Agency spokesman said extra staff members had been drafted in and "officers worked as quickly as they could to clear passengers".
A weather warning for dense fog had also been issued for Yorkshire and Humberside, the East and West Midlands, the East of England and the South East.
European flight management agency Eurocontrol was reporting severe delays because of the weather across Europe - especially at airports in Amsterdam, Brussels, Vienna, Oslo, Paris and Zurich.