Around 1,000 Border Force members of the Public and Commercial Services union will strike over 23-25 December, returning to work at 7am on 26 December, and again over 28-30 December, returning to work at 7am on 31 December.

The action will take place at Birmingham, Cardiff, Gatwick, Glasgow, Heathrow and Manchester airports. Soldiers and civil service volunteers will stand in to conduct some border checks, but passengers arriving into the UK via any of these airports have been warned to expect longer wait times.

Aviation consultant John Strickland told the BBC that Heathrow would likely face the biggest issues due to its scale and the number of long-haul flights it welcomes every day, passengers of which are typically subject to more border checks.

Strickland said Heathrow’s traffic composition was geared towards more worldwide arrivals compared to Gatwick, for instance, which is predominantly short-haul and is likely to have a higher number of passengers who can use airport eGates.

Speaking to BBC Radio 4’s Today programme, Gatwick head of passenger operations Adam Jones forecast the worst case scenario at the Sussex airport would be waits of up to two hours at passport control.

Some 10,000 passengers were expected to arrive at Heathrow before 7am on Friday, something Border Force briefed it had built into its contingency plans. Other airports, though, have warned of potential cancellations.

Earlier this week, Border Force chief Steve Dann played down the most severe predictions of disruption, claiming the unit had undertaken extensive planning over several months working in partnership with the travel industry and ports to mitigate the impact of strike action.

Dann said airport closures were possible but unlikely. “We have a reasonable expectation that we will be able to deliver a service that keeps most, if not all, ports open,” he said, but admitted: “Our contingency workforce will not be able to operate with the same efficiency."

PCS union members are in dispute with the Home Office, which is responsible for Border Force, over pay, pensions, jobs and redundancy. The union said it was standing in solidarity with other works staging strike action over the festive period, including nurses, ambulance workers and train drivers.