Air passengers could face a second day of flight cancellations and delays tomorrow as more snow is on its way, airlines said today
Travellers were advised by airline operator BAA to check with their airlines before setting off, while British Airways (BA) and Ryanair said another day of disruption was possible.
Nearly 800 flights were cancelled at Heathrow today due to heavy snowfall and others were subject to long delays.
About 200 Ryanair flights into and out of the UK were cancelled, mostly at Stansted, and all BA flights from Heathrow were cancelled until 5pm, spokesmen for the airlines said.
With the Met Office forecasting further sleet and snow in parts of England, Scotland and Northern Ireland, travellers could have a tough time of it tomorrow.
A BA spokesman said: "It's too early to say what the situation will be, but there will be some disruption.
"The forecast isn't good but it remains to be seen how many flights we can get up today.
"Every airline operating from Heathrow will have some disruption. We're very dependent on what happens with the weather and with heavy weather forecast it puts us in a very difficult position."
A Ryanair spokesman said: "At the moment we're hoping the airports will operate tomorrow but (our flights) will be subject to whether we can get our aircraft back in.
"Some of our planes are stuck in Birmingham airport, which is closed.
"I think it's likely we'll see disruptions due to the severe weather conditions forecast."
Flights were also cancelled or delayed at airports including Gatwick, Luton, Southampton, Leeds Bradford and Newcastle today.
London City Airport was closed.
BAA said the airport was using many of the 58 snow ploughs, snow blowers and other specialist vehicles in its fleet as it fought to reopen the runways.
Airlines have offered passengers the choice of rebooking their cancelled flights or receiving a refund.Reuse content