The busiest day of the Christmas travel rush is expected on Friday as about 19 million drivers take to Britain’s major roads. Friday will also be the peak time for passengers heading abroad, with Heathrow airport and on Eurostar expected to be especially busy.

Gatwick had expected its busiest day to arrive on Sunday, but now could be dealing with a backlog of disruption after drones grounded all flights on Thursday.

According to the AA motoring organisation, the combination of the Christmas holiday getaway from work and school, combined with last-minute shopping, will make Friday the UK’s busiest day on the roads, especially in Northern Ireland and the English regions.

More than half of the 20,000 drivers it surveyed said they would also travel on Saturday, with traffic tailing off before Christmas Eve.

The RAC and traffic analyst Inrix said Friday would see the peak of additional leisure trips for Christmas, bringing an extra 2.8m cars to the roads on top of everyday commuter traffic.

It warned of significant delays on the M6 and M40 in particular, with some of the worst tailbacks forecast on motorways in the West Midlands on Friday and Saturday. The anticipated traffic jams could be compounded as rail disruption forces more people on to the roads, the RAC said.

As well as the usual railway shutdown for 25 and 26 December, engineering works and strikes will limit some rail services over the Christmas and New Year holiday period. Network Rail said it would carry out work worth £148m on 330 projects over the festive holidays, but that the majority of the railway system would be unaffected.

However, all lines out of London Paddington will be closed on 23, 24 and 30 December, while work will also close the line between London Victoria and Clapham Junction from Sunday to the new year, meaning that the Gatwick Express will not run. Some Thameslink and East Midlands rail services north of St Pancras will also be affected by engineering.

The RMT union is planning to continue strikes on Northern rail each Saturday, as well as South Western railway on 27 and 31 December.

Coach operator National Express said it would be adding more than 50,000 extra seats to its services over the festive period, as it is the only national public transport network running on Christmas Day.

Around 4.7 million passengers were set to fly abroad on holiday from UK airports over the festive period. Heathrow, Britain’s biggest airport, expects 134,000 of more than 1 million departing passengers to fly on Friday, its busiest day, with New York, Dubai and Amsterdam being the most popular flight destinations.

Eurostar, the cross-Channel train service, expects to carry almost 5% more passengers over this Christmas than a year ago, with nearly 19,000 departing from the UK on Friday.