Simon Calder: Flown from the freeze? You’re one in a million

Are you reading this on the beach or on a ski lift? At 35,000 feet or 186mph? If so, congratulations. You have already made your escape from a nation that, according to the forecasters, is set for the opposite of sun, sand and sea: expect snow, sub-zero temperatures and seizing up.

I estimate you are one in a million; from a week of phoning around the country's transport operators, that seems the likely number of Brits who have already left the country to celebrate Christmas in a location where midwinter may be a touch less bleak and where de-icing fluid constitutes a tasty-if-lurid cocktail rather than a chemical compound.

In a normal year, 18 December would represent little more than an overture, marking the start of a great getaway that builds to a travel crescendo two or three days before Christmas Day. But the fact that 25 December and New Year's Day are both Saturdays has distorted travel patterns through the festive break.

The skiing market is in some disarray due to 25 December and 1 January falling on the main "changeover day", Saturday. And it appears that many families have seized the chance to grab a pre-Christmas week away. At some of Britain's top airports, and on international trains from London St Pancras to Paris and Brussels, the biggest crush of the season ... has already happened. Friday, 17 December was the day of the greatest escape.

Where I live, the schools broke up yesterday afternoon. But judging from the figures provided from sources as diverse as BAA, Eurostar and easyJet, there must have had a good few empty desks: even allowing for yesterday's cancellations at Heathrow, 200 passengers per minute were booked to pass through Britain's busiest airport during its operating hours.

That still leaves a good three million of us who have plans to travel abroad over the festive season. Tell me which escape route you are using, and I shall predict when you are likely to leave – and return.

Unlike forecasts of road traffic and rail passengers, airlines and airports know to a high degree of certainty how many travellers are likely to fly in and out.

Today Heathrow and Gatwick will be full of Virgin Atlantic and British Airways long-haul passengers waiting anxiously for de-icing (for the aircraft, not for themselves). But other airlines have different peaks: Monarch planes are busiest on Thursday 23 December. The airline expects another surge a week later; on 30 December, people coming home from Christmas away will swap places with those resolving to start the New Year as they plan to continue, ie on holiday (well, that's my intention, at least).

Going to Gatwick tomorrow? You won't be alone, since 19 December is set to be the Sussex airport's busiest day this month.

Many other airports are available, which is a blessed relief to all of us. Edinburgh and Glasgow were expecting their maximum passengers yesterday, weather permitting – a phrase that has attached itself like a snow chain to Scotland this month. Manchester hits a peak on Wednesday 22 December, with a winter sports-related spike (or should that be a ski pole?) predicted for Boxing Day. Luton, Birmingham and Cardiff airports expect bumper bookings on 27 December.

Even Christmas Day is looking lively at Heathrow and Gatwick, which will process precisely a Wembley Stadium-full of passengers: 90,000 in total. Heathrow is the only UK location with a scheduled train service on 25 December (half-hourly from Terminals 1 and 3 to 4 and 5, free).

My tip for 25 December: enjoy the wide, open spaces of Stansted. The Essex airport anticipates only 2,000 passengers all day – on its busiest day, next Thursday, that's a mere 40 minutes' worth.

New Year's leave

Talking to airports and airlines, it seems as though an air-traffic map of Britain on 2 January will resemble a particularly scary video game, with everything converging on the UK at once. Almost every airport expects it to be their busiest day of the season.

The day after New Year looks like a hangover for everyone. Airport and airline staff will be at full stretch, while passengers expecting short lines for passport control and their bags already waiting on the carousel may be disappointed. The crush is likely to be most intense at Heathrow and Gatwick early that Sunday morning: Virgin and BA long-haul flights from the world's sunniest spots are going to be rammed.

You can't say quite the same about Britain's offices, factories and classrooms the following week. Virgin Atlantic reports that the following weekend, 7 and 8 January, is almost as busy as 2 January – suggesting many of you have cancelled the milk for a long-haul escape of two or three weeks. Good call.