Disruption caused by dense fog was expected to continue at Gatwick airport until the end of Sunday – its busiest day of the holiday period.
Nats, the UK’s main air traffic control provider, said temporary air restrictions were in place for the remainder of the day because of low visibility in airfields affected by fog.
Earlier easyJet said a number of flights had been delayed or cancelled due to the knock-on impact of delays caused by the weather.
It follows two days of disruption at the UK’s busiest airports, with Saturday’s flights at Stansted affected by the murky conditions while live departure boards showed delays at Heathrow, Luton, Gatwick and Manchester airports.
On Sunday morning, a spokesperson for Gatwick said temporary air traffic restrictions remained in place because of poor visibility caused by fog and warned that some flights could be delayed throughout the day.
A total of 769 flights were planned at the West Sussex airport on Sunday, making it the busiest day of the Christmas holiday period.
Passengers were urged to contact their airlines for updated information.
A Nats spokesperson said: “While the weather conditions have improved, fog continues to affect some airports in London today.
“Temporary air traffic restrictions are therefore in place at airfields with low visibility to maintain safety.
“Our teams are working closely with the airports and airlines to minimise disruption but passengers should check the status of their flight with their airline.”
Patches of thick fog could reduce visibility to just 100 metres in some areas, the Met Office said.
Heathrow, Luton and Stansted airports said flights had not been affected by the weather.
A spokesperson for easyJet said: “We are doing all we can to minimise the impact of the weather for our customers, providing options to rebook or a refund for cancelled flights, as well as hotel accommodation and meals where required.
“We advise customers due to travel to and from London Gatwick today to check our flight tracker for the latest information on their flight.
“The safety and wellbeing of our customers and crew is our highest priority and, while this is outside of our control, we are very sorry for the inconvenience caused by the weather.”
Passengers on flights delayed for more than two hours may be entitled to assistance, including food and drink or overnight accommodation if necessary.
Kiera Quayle, from Colchester, Essex, was due to fly from Isle of Man airport to Gatwick on Friday evening with her husband after visiting his family.
But their flight was delayed by three hours before finally being cancelled at around 10pm, with the next one not available until Sunday.
“Our five days has turned to seven, it looks like,” Quayle, 30, told the PA news agency.
“It’s frustrating and stressful but I overheard a few families who are now missing holidays and work who have it worse at this point.”
