The Met Office has issued a yellow severe weather warning for snow across London, which includes anticipation of widespread ice overnight.
From 3pm on Thursday January 12, dozens of flights have been cancelled including flights to Manchester, Geneva, Frankfurt and Amsterdam.
Taking to Twitter, Heathrow Airport sent out a warning to passengers: "Wintery weather is expected at the airport today and airlines will be adjusting their schedules as a result.
"Check your flight status if travelling and allow more time to get to the airport.
"We are sorry for any disruption."
British Airways is also warning of disruption.
The airline has notified passengers not to come to the airport unless they have a confirmed booking on a flight that is operating.
"As a result of the forecast poor weather we have agreed with Heathrow Airport, National Air Traffic Services (NATS) and other airlines to reduce the afternoon and early evening flight schedules at the airport on Thursday 12 January," BA said.
"The number of aircraft permitted to land by NATS at the Heathrow Airport from 3pm on Thursday is likely to be significantly reduced as the airport’s ground teams may need to remove snow and ice from the airport’s two runways and multiple taxiways.
"We are sorry for the difficulties which are likely to be caused by the poor weather and will do all we can to minimise the effect it has on our operations."
It also warned that flights to and from London Gatwick and London City airports may be affected.
Dutch airline KLM also reported disruption, saying on its website: "Because of weather conditions expected in London, flight schedules may be disrupted."
Airlines including Virgin Atlantic, British Airways and KLM are inviting affected passengers to rebook on an alternative flight.
Heathrow Airport has the following advice on their website for passengers:
"If your airline cancels your flight the airline must give you the option of rebooking an alternative flight; either as soon as possible, or at a later date.
"If no flight is suitable you can request a refund."
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