Heavy snow halts Gatwick Airport flights
All flights at Gatwick Airport have been cancelled until 1000 GMT on Thursday after snow and ice forced the closure of the runway.
Passengers have been urged not to travel to the West Sussex airport and instead contact airlines to find out when individual services will resume.
Met Office heavy snow warnings have been put in place for the South East.
Up to 10cm could fall in places on Wednesday evening and into Thursday with Sussex being badly affected.
More than 150 schools have been shut because of the wintry conditions in East and West Sussex.
There are also delays on the road and rail networks.
Southeastern trains said it had introduced a contingency timetable on Wednesday and Thursday.
A spokesman said: "We would encourage all passengers to leave London earlier than usual, before bad weather arrives in the South East."
A spokeswoman for Gatwick Airport said: "Due to severe weather conditions, there will be no departing and arriving flights at Gatwick today or overnight.
"The runway will remain closed until at least 1000 [GMT] on Thursday.
"There will be significant disruption, delays and cancellations tomorrow and passengers should not set out for the airport before checking with their airline for the latest information."
She said there were a number of passengers at the airport and they were being looked after.
The runway was closed at 2230 GMT on Tuesday.
Some flights were diverted to Luton Airport in Bedfordshire earlier on Wednesday with passengers then being driven by coach to Gatwick Airport.
Gatwick said it had recently spent £300,000 on de-icing and snow-clearing vehicles.
BBC Oxford reporter Emma Vardy who was due to fly to Gatwick from Madrid was told she would not able to travel.
She said: "I was told that the earliest flight I would be able to return on was Saturday, but passengers behind me were told they may not fly home until as late as Monday or Tuesday of next week.
"Some decided to get refunds on their flights, others opted to transfer onto flights to Paris in the hope of catching the Eurostar back to the UK.
"Eventually the airline began handing out hotel vouchers to stranded passengers so that they could find a place to stay until the next available flight and gradually passengers began to leave the airport."
'Rural routes treacherous'
Sussex Police urged motorists to only travel if their journey was absolutely necessary.
Ch Supt Paul Morrison said: "As night falls and temperatures drop, driving conditions in many areas, especially rural routes, are treacherous and with more snow forecast by the Met Office, I would suggest that you should not be driving unless it is absolutely essential.
"At best, your trip could be long and stressful, at the worst you could find yourself involved in an incident that may or may not be of your making."
BBC South East Today's weather forecaster Kaye Forster said: "It's set to get a lot worse before it gets better."
She said a further 10cm (4in) of snow was possible overnight with freezing temperatures making the conditions on the roads "horrendous".
By Thursday, some areas may see up to 25cm (10in) of snow with temperatures hovering around freezing.