Passengers are warned to prepare for the Christmas travel chaos as a Border Force strike begins on Friday.
About 1,000 PCS union members working in passport booths will be out, causing disruptions at major airports like Gatwick and Heathrow.
The action is expected to delay around 250,000 arriving passengers during the busiest Christmas time for airports since 2019.
Heathrow, the UK’s busiest airport, with around 579 flights to land on Friday, could be hit worst.
Around 10,000 passengers are expected to arrive just before 7am, and the first flight – a British Airways service from Cape Town – will land at 4:45 AM.
The airports of Birmingham, Cardiff, Gatwick, Glasgow and Manchester and the port of Newhaven were also affected. Picket lines will be installed outside.
Delays in checking the passports of arriving passengers can result in long queues and even people being held on board and delayed departures.
Border Force chief of operations Steve Dann had previously acknowledged that military personnel and public service volunteers would not be enough to limit the outage.
He said that while “strong plans” are in place, “the contingency workforce cannot operate with the same efficiency as our permanent workforce.”
Electronic passport gates will remain open but cannot be used by all passengers, such as children under the age of 12.
Industrial action by National Highways staff continues on Friday, as the country’s rail network will come to a complete standstill on Christmas Eve due to the strikes.
Border Force attacks will continue from December 23 to New Year’s Eve, except for December 27.
It is estimated that around two million passengers are booked to fly to the affected airports during the marches.
It comes amid a long-running dispute with the Interior Ministry over salary, pensions and conditions.
PCS general secretary Mark Serwotka told people affected by the disruption to direct their anger at the Government.
“If the government puts more money on the table it can stop these strikes tomorrow,” he said. “Like many workers, Border Force workers are battling the cost of living crisis. They are hopeless.”
Paul Charles, CEO of travel consulting firm The PC Agency, said: “What worries travelers is the uncertainty as they have no idea how the strikes will affect their arrival experience.
“Many are likely to face longer queues and delays this festive period, and some may find themselves stranded on inbound aircraft before they are allowed to enter the terminals.
“Let’s hope border guards can process all passengers smoothly and without worries.”