Border Force strikes threaten misery for millions of passengers arriving at UK airports during the first restriction-free Christmas in three years.

Under contingency plans being drawn up, passengers will be held on aircraft to prevent overcrowding in airport arrival halls during the strikes.

Officials also fear that passengers could be made to wait more than two hours in queues at passport control as strikes hit the peak Christmas holiday period. More than 1,000 members of the Public and Commercial Services (PCS) union employed by the Home Office to staff passport control desks are due to strike from Friday.

The action will affect Heathrow, Gatwick, Manchester, Birmingham, Cardiff and Glasgow from December 23 to Boxing Day and from December 28 to New Year’s Eve. More than 10,000 flights are scheduled to land at the airports over the affected dates, equating to two million airline seats.

Officials are most concerned about the second wave of action, when hundreds of thousands of holidaymakers who have been abroad for Christmas return home, raising the prospect of huge bottlenecks at immigration.

“Border Force are talking about moving staff around the country and the government are looking at drafting in over 1,200 soldiers, but it is a very busy period,” a source involved in discussions said. “Delays of two hours at the border are being routinely discussed in meetings. If everything backs up, or anything [such as e-gates] fails, then airports will have to instruct that passengers are held on planes to prevent overcrowding.”

Britain faces a further wave of strike action this week as nurses, ambulance drivers and driving examiners walk out. Workers at the Department for Work and Pensions will strike today and National Highways workers, including control room staff and traffic officers, will take industrial action from Thursday to Christmas Day.

Airports are gearing up for their busiest Christmas in three years and the first without restrictions since 2019. More than five million Britons are due to travel abroad over the festive period, according to the travel trade body Abta.

The Civil Aviation Authority warned passengers that the strikes could lead to long queues as well as flight disruption. Paul Smith, the regulator’s consumer director, said: “We expect airlines to do what they can to minimise the overall disruption to passengers, and this includes providing passengers with updates and information about their rights when flights are disrupted.”

British Airways and Virgin Atlantic are understood to have stopped selling inbound tickets to Heathrow on strike days after talks with the airport.

Aviation bosses are especially concerned about the knock-on effect that the strikes could have, especially if passengers are held on aircraft. “Christmas and new year are always volatile times,” a source said. “Tensions run high at the best of times and that’s before strikes are in the equation.”

Airlines could have to cut passenger volumes by up to 30 per cent if airports become overwhelmed. In a letter to aviation bosses Phil Douglas, director-general of Border Force, wrote: “Our contingency workforce will not be able to operate with the same efficiency as our permanent workforce.”

Congestion is also expected on the roads, with motoring groups predicting drivers will embark on about 20 million car journeys to see friends and family over Christmas.

Further rail disruption is expected after an overtime ban for 40,000 RMT members came into force yesterday, with last-minute cancellations expected across the network. Strikes by workers at Network Rail are planned from Christmas Eve, with services expected to stop from early afternoon.