Thousands of air passengers are facing days of disruption after flights from Scotland to London Heathrow were cancelled due to dense fog.
Passengers have been warned to expect further delays
A total of 47 flights from Glasgow, Edinburgh and Aberdeen were affected and all BA domestic flights to and from Heathrow will be cancelled on Friday.
Train and bus companies said they were already busy and running to capacity.
A BA spokesman said passengers would be able to re-book but it could take 48 hours to clear the backlog.
Denny McGee urged passengers to check if their flight had been cancelled before travelling to airports.
He said: "Previous disruption for other reasons and for weather has shown us that it takes some time to get back to normal.
"I think 48 hours would be probably an optimistic view of it but obviously we'll work very hard to get the service back to as smooth an operation as soon as we possibly can.
"But I think passengers should be prepared for further disruption over the next perhaps 48 hours."
BAA said there were 47 cancelled departures from Scotland - 17 from Glasgow, 20 from Edinburgh and 10 from Aberdeen.
Some flights operated by BMI Baby and FlyBe to London, Cardiff and Southampton have also been cancelled.
Many Scots travelling home for Christmas were also stranded in London as northbound flights were also scrapped.
Bishop David Chillingworth was caught in the disruption as he travelled back from Stockholm to Edinburgh.
He told BBC Radio's Good Morning Scotland programme: "The flights were running late at Stockholm so we got on a delayed flight and arrived in Heathrow in the middle of all this without any advanced warning.
"We discovered that the only flight back to Edinburgh was full and all the rest were cancelled."
The bishop said he managed to book a sleeper train back to Scotland but had to leave his bags at Heathrow.
"We didn't have to go to Heathrow and yet were allowed to do that so that the chaos was worse and when you want to find out how to get your bag you end up queuing," he added.
The days in the run-up to Christmas are amongst the busiest of the year at Scotland's airports.
About 3,000 people in Scotland were affected by Wednesday's cancellations, with many more facing delays as people started to travel home for Christmas.
However, forecasters said the foggy conditions were beginning to improve at Gatwick and were expected to improve at Heathrow.
The disruption has hit at one of the busiest times of the year
BA operates 29 flights from Scotland to Heathrow daily: 12 from Edinburgh; 10 from Glasgow and seven from Aberdeen.
The three airports are expected to handle 194,000 passengers in the coming days, with a further 213,000 travelling in the lead-up to Hogmanay.
Friday was expected to be the busiest day of the festive season, with 81,000 passengers across the three airports.
BA passengers are being urged to check the airline's website or call 0800 727 800.
Train operator GNER advised people to travel off peak and keep luggage to a minimum.
Low-cost bus operator Megabus has more than doubled capacity on its London to Glasgow service.
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