THE Christmas travel plans of tens of thousands of Scottish families are in doubt, after experts warned severe disruption to air and road networks would continue until the weekend.
• Shoppers braved the conditions in Edinburgh yesterday
The dire news came after a nightmare weekend for travellers in which the Met Office took the decision to issue a rare "red flash" weather warning for parts of Scotland.
Police in the Lothians and Borders advised travel only if it was "essential" and even cautioned people about the wisdom of Christmas shopping.
Almost 300 Scottish flights were grounded on Saturday and Sunday, leaving many aircraft out of position for the crucial pre-Christmas rush. The severest winter weather for a century also played havoc with schedules at Heathrow and Gatwick, with officials warning of further disruption "in the days that follow".
With most flights this week already full during what is the busiest period of the year, many face the prospect of cancelling trips or making the journey by road and rail.
Scott Allison, from Glasgow, said: "I'm stranded in Amsterdam. When will I get home? I have no idea."
Significantly, the weather forecast in the run up to Christmas Day includes warnings of further snow, which could slow overground travel.
Bookmaker Ladbrokes was offering odds of 11/10 that snow will fall in Edinburgh and Glasgow on Christmas Day.
Most schools across Scotland are expected to open today, although parents are advised to check with their local authority this morning. But Aberdeenshire Council said several schools would be closed, while Aberdeen and Midlothian planned to open some schools later than normal.
The Arctic conditions have already hit Scotland's retail sector, with fewer shoppers out on "super Saturday" compared to last year, and stores are now planning to extend opening hours to make up for lost sales. The east of the country was the worst affected, with up to 10cm of snow falling in Edinburgh and East Lothian.
But it was travellers who had to cope with the worst of the disruption. As airlines seek to move diverted aircraft and crew back to their normal positions, there are warnings the backlog may not be cleared before Christmas.
• Click here for more coverage of Scotland's Big Freeze
Aviation expert Jim Ferguson said: "Given the severity of the snow we're seeing and the fact it's coming in near-regular squalls makes it difficult to find a window for flights, it's a near-impossible job.
"It couldn't have come on a worse weekend. It's possible the backlog could be cleared in time for Christmas - the airlines will do what they can.
But if they get more snow, they'll be stuck."
Edinburgh airport closed yesterday at 10:30am, reopening for departures only at 2:30pm before taking inbound flights. Scheduled services faced delays of up to seven hours, while 112 flights were cancelled. The airport also took in five Heathrow-bound flights that had to be diverted. Some 52 flights were cancelled on Saturday.BAA Edinburgh, said about 80,000 people had been due to pass through the airport from Friday until today, but "not too many" had reached their final destination.
There were delays of five hours at Glasgow airport, where some 30 flights were cancelled yesterday and 44 on Saturday.
Aberdeen airport cancelled about 40 flights, after closing early yesterday for "essential de-icing" before reopening at midday. It suspended operations again for an hour from 2:30pm, with delays of up to five hours for scheduled services. Airports in the Highlands and islands also endured delays of several hours.
The worst of the disruption was seen at Heathrow. After closing on Saturday, heavy snow in the London area meant it was not allowing any flights to land on its runways, with only a "handful" of departures yesterday. Thousands of holidaymakers were preparing to bed down for a second night there, with many complaining of a lack of information.
Many travellers took to social networking site Twitter to vent their frustration. One, Weared0, wrote: "Stuck in Bristol airport....Glasgow flight just cancelled...fingers crossed Edi flight does not go the same way..."
Others voiced fears they may not be able to reach their destinations before Christmas. MichPiano wrote: "Now following Edinburgh Airport on Twitter out of fear for spending Christmas in a departure lounge..." Another, activwebwendy, wrote: "Hoping the snow will go so I can get away for Christmas tomorrow .Anyone actually got away today from Edinburgh Airport?"
Trevor Taylor, 37, who waited with his wife and two young sons for two days for a flight to Singapore, said there was "absolute mayhem" in Heathrow's Terminal 5.
He said: "There are kids that haven't been fed, elderly people in wheelchairs getting cold.
"It's 'everyone fend for yourself.,"
Gatwick airport reopened after its planes were grounded for much of yesterday, but widespread disruption remained.
Balpa, the pilots' union, accused Britain's main airports of running a "third world" operation during the big freeze.
BAA spokesman Andrew Teacher apologised for the "miserable" situation but said problems had been caused by "an extreme amount of snow in a very short space of time" and safety had to be prioritised.
British Airways said "several thousand" of its stranded passengers were being put up in hotels, but when asked if the company was confident of getting everyone to their festive destinations, a spokeswoman said: "We are in the hands of the weather."The heavy snow caused chaos across Europe, with flights cancelled at Frankfurt, Paris, Florence and Amsterdam.
The rail network also saw widespread problems, with numerous cancellations of ScotRail services and delays of up to an hour. Services on the east coast mainline were suspended between London and Peterborough because of a power failure, and East Coast ticket holders were advised not to travel.
There were also delays on Virgin train services to and from Scotland.
Across the nation's roads, the snow led to several route closures and widespread delays.
In the Edinburgh area, the A720 city bypass was reduced to one lane eastbound, while the northbound lane of the Dolphingstone flyover was closed for a while yesterday morning after an accident.
A spokesman for Edinburgh City Council said priority was being given to main roads with 22 gritters, 16 mini-tractors and 32 other vehicles clearing snow.