Passengers are being warned to prepare for Christmas travel chaos on Friday as a Border Force strike begins.
Around 1,000 PCS union members who are manning passport booths will walk out, disrupting major airports such as Gatwick and Heathrow.
The action is expected to cause delays for around 250,000 incoming passengers in the busiest Christmas period for airports since 2019.
Heathrow – the UK’s busiest airport, where some 579 flights are due to land on Friday – could be the hardest hit.
Around 10,000 passengers are expected to arrive before 7am alone, with the first flight – a British Airways service from Cape Town – due to land at 4.45am.
Birmingham, Cardiff, Gatwick, Glasgow and Manchester airports, as well as the port of Newhaven are also affected. Picket lines will be set up outside.
Delays in checking the passports of arriving passengers could lead to long queues and even people being held up on planes, delaying departures.
Border Force chief of operations Steve Dann earlier acknowledged that military personnel and civil service volunteers would not be enough to limit the disruption.
He said that until “solid plans” are in place, “the emergency workforce will not be able to operate with the same efficiency as our permanent workforce”.
The doors of the electronic passports will remain open but they will not be able to be used by all passengers, such as children under the age of 12.
Industrial action by national highway staff will also continue on Friday, while the country’s rail network is set to come to a complete halt on Christmas Eve due to strikes.
The Border Force strikes will continue from December 23 until New Year’s Eve, with the exception of December 27.
It is estimated that around two million passengers are booked to fly at the affected airports during the walkouts.
It comes amid a long-running dispute with the Home Office over pay, pensions and conditions.
PCS General Secretary Mark Serwotka told those affected by the disruptions to direct their anger at the government.
“The government could stop these strikes tomorrow if it puts more money on the table,” he said. “Like so many workers, Border Force employees are grappling with the cost of living crisis. They are desperate.”
Paul Charles, chief executive of travel consultancy The PC Agency, said: “It’s the uncertainty that passengers are worried about, as they have no idea how the strikes will impact their arrival experience.
“Many are likely to face longer queues and delays during this festive period, and some may find themselves stranded as planes arrive before being allowed into terminals.
“Hopefully the border authorities can process all passengers smoothly and without worry.”