Heathrow is set for its busiest day of the year so far / Leon Neal/AFP/Getty Images

New York JFK is top destination with  Dubai overtaking Edinburgh as runner-up

The big summer getaway has begun, with Thursday provisionally reckoned to be Heathrow's busiest day so far this summer for outbound travellers. Almost 121,000 outbound passengers are expected. Friday is forecast to hit the same score.

Between Heathrow's first departure at 6am, and the last shortly before 11pm, an average of two passengers a second will fly out of Europe's busiest airport. Most flights were operating normally, though British Airways cancelled departures to Dallas and Cairo.

The leading destination, by a wide margin, is New York JFK, with 9,170 passengers predicted. Edinburgh has been overtaken for second place by Dubai, which at around 6,180 passengers is 430 ahead of the Scottish capital - equivalent to a nearly full Airbus A380.

At Gatwick, Friday is expected to be the busiest day, with 72,000 passengers expected. The top four destinations are all in Spain: Palma de Mallorca is easily the most popular, ahead of Malaga, Barcelona and Tenerife. More than 500 holidaymakers were obliged to spend the night at the airport after a Monarch flight to Larnaca and a BA flight to Orlando were delayed overnight. Gatwick passengers on some easyJet services to and from Berlin and Geneva faced delays.

Manchester airport anticipates handling about 40,000 passengers on each day of the weekend. Palma is also the top destination. In second place, though, is Heathrow - where almost every passenger is connecting. Dalaman, the airport for Turkey's Mediterranean coast, is in third place. The top five is completed by Tenerife South, the airport for the largest Canary and Alicante - the gateway for Benidorm.

More than 100,000 travellers are expected to fly from Scottish airports over the weekend, with 50,000 from Glasgow alone.

The busiest three days for the leading British port, Dover, are expected to be Thursday, Friday and Saturday. Over those three days, P&O Ferries expects to take more than 100,000 outbound passengers to Calais. The peak for returning holidaymakers across the Channel is the weekend of 31 August and 1 September.

Eurostar, which runs trains from London St Pancras to France and Belgium, predicts a total of 70,000 passengers over the weekend. On domestic trains, close to five million journeys are expected on Friday.

Abta, the travel association, calculates that two million British holidaymakers will head overseas between Friday and Sunday - but many families have decided to stay in the UK. Abta's chief executive, Mark Tanzer, said: "The recent amazing weather at home has also given a great boost to domestic tourism".

David Bizley, technical director of the RAC, said: "Frankly, anywhere that heads to the coast is likely to be busy". Particular stress is likely to fall on the M5, A30 and A303 to the West Country; the A55 in North Wales; the M55 to Blackpool and the A47 to Great Yarmouth.

For motorists heading to France, the following weekend is predicted to be worst of the year on the motorways from Paris to the south. On the first Saturday in August, "extremely difficult circulation" is predicted.