Freezing fog has forced Heathrow Airport to cancel up to 100 flights.
The reduced visibility gave the airport no choice but to cancel approximately 100 out of about 1,300 flights, according to a spokesman.
Heathrow’s normal pattern of a plane landing or taking off every 45 seconds is impossible under the foggy conditions.
It is another day of disruption for travellers after around 100 flights were cancelled at Heathrow on Monday, while there were also problems at Gatwick, London City, Stansted and Southampton airports.
A Heathrow spokesman said: “Persistent freezing fog across the south east has reduced visibility at Heathrow again today.
“With Heathrow operating at more than 99% capacity, there are no gaps in the schedule that can be used for delayed flights and as a result, some passengers may experience disruption to their journeys today.
“Passengers should check their flight status with their airline before coming to the airport. As always, Heathrow’s top priority is the safety of passengers and we apologise to those whose travel has been affected by today’s weather.”
The Met Office said a “severe” warning was covering all of England, except for the North East, and south-east Wales and will remain in place until 11am on Tuesday.
A Gatwick spokeswoman said: “Air traffic control restrictions imposed due to fog across the South East and Europe may cause some delays to flights.”
Edinburgh Airport advised passengers to contact their airlines after flights towards the south of the UK were affected yesterday.
Bristol Airport said flights were operating as normal while Stansted said it had no cancellations yet, but urged passengers to contact their airlines for the latest information.