Airports appeared to be coping with a strike by Border Force staff on Friday after military stepped in to check passports.
About 1.8 million travellers arriving at UK airports over Christmas have been warned to expect delays.
Heathrow, Birmingham, Cardiff, Gatwick, Glasgow and Manchester airports, and the port of Newhaven in East Sussex will be affected as about 1,000 members of the Public and Commercial Services union employed by the Home Office walk out.
The Border Force strikes by those working the passport desks will take place every day from Friday to the end of the year, except December 27.
This coincides with strikes by rail and highways workers, making travelling over Christmas in the UK a potential nightmare.
Airports have put in measures to limit disruption which would likely affect those travelling with children. Electronic passport gates will remain open but some passengers, such as those aged under 12, cannot use them.
Aviation data company Cirium said 1,290 flights are scheduled to land at affected airports on the first day of industrial action, with a total capacity of more than a quarter of a million passengers.
This is the busiest Christmas for airports since 2019, as it is the first festive period without coronavirus restrictions since the start of the pandemic.
Around a quarter of a million passengers are arriving on flights at affected airports on Friday, including approximately 10,000 people who landed at Heathrow before 7am.
There are fears that delays in checking the passports of arriving passengers could lead to long queues and people being held on planes, disrupting later departures.
However, Adam Jones, head of passenger operations at Gatwick, told Radio 4’s Today programme there was “plenty of space in the terminals to manage large queues”.
“The worst case we see is potentially two hours, however we have extra staff in the airport to look after passengers’ welfare,” he said.
“We do have the ability to control the traffic to the airport if the situation requires it, but at the moment we don’t expect to use that.”
On Friday morning arriving passengers were being processed “as normal” at Gatwick, said an airport spokesman.
“Everything is going OK at the moment,” he added.
“There’s plenty of staff. The e-gates are all operating. It’s going well. There’s no delays as far as we’re aware, and no queues at the moment. I’m standing in arrivals and passengers are flowing through as normal.”
UK strikes — in pictures
Military personnel and volunteers from the Civil Service have been trained to step in.
Border Force head of operations Steve Dann said on Wednesday that there were “robust plans in place” to limit the effects of the strikes, but the “contingency workforce will not be able to operate with the same efficiency as our permanent workforce”.
Mr Dann said the organisation could not predict the extent of any delays to passengers, but “people should be prepared for disruption”.
Nurses strike in the UK — in pictures
The Border Force strikes are part of a rolling programme of industrial action by members of the PCS union in a long-running dispute over pay, jobs, pensions and conditions.
PCS general secretary Mark Serwotka said the action was a “last resort”.
He said 40,000 of its members were using food banks and 45,000 of them were claiming in-work benefits.
“They are the in-work poor. We presented the government with a dossier where their own staff spoke to the government,” he told the Today programme on Friday.
“After months trying to persuade them otherwise, is a 2 per cent pay offer.”
He said travellers could face months of disruption unless the government comes forward with an improved pay offer.
Mr Serwotka predicted a “huge escalation” in industrial action in January across the Civil Service unless ministers enter into negotiations.
“We think that the action at the borders is going to be very effective,” he said. “We hope that the government will therefore do the right thing and get around the negotiating table and put some money upfront.
“If not, we are raising money, we have a strike fund that means we can sustain this action. Our strike mandate lasts right up until May. We will be supporting this action up to May and we would re-ballot again if we have to.
“I think in January what you will see is a huge escalation of this action in the Civil Service and across the rest of our economy unless the government get around the negotiating table.”
Picket lines will be set up outside airports affected by the strike on Friday morning.
UK Prime Minister Rishi Sunak said: “I am really sad and I am disappointed about the disruption that is being caused to so many people's lives, particularly at Christmas time.
“When it comes to the difficult question of setting public pay, the government has acted fairly and reasonably in accepting all the recommendations of the public sector pay review bodies.”
“I would urge everybody who is travelling at the moment to just please check before you make your journey so you know what it happening.”
Mr Sunak has insisted that not negotiating on pay with striking workers is “in the long term” is the “right thing for the whole country”.
UK rail strikes cause disruption for millions amid cold snap — in pictures
Cirium said 8,910 arriving flights with a combined capacity of nearly 1.8 million seats are scheduled at affected airports across all of the strike days.
Many airline passengers will also be affected by a strike by thousands of members of the Rail, Maritime and Transport union at Network Rail on Christmas Eve, which will cause train services to stop running at about 3pm.
London tube strikes — in pictures
“It’s the uncertainty that is worrying passengers, as they have no idea how the strikes will impact their arrival experience,” said Paul Charles, chief executive of travel consultancy the PC Agency.
“Many are likely to face longer queues and delays during this festive period, and some could find themselves stuck on arriving aircraft before being allowed into the terminals.
“Let’s hope that border officials can process all passengers smoothly and without worry.”
Julia Lo Bue-Said, chief executive of the Advantage Travel Partnership network of more than 700 UK travel agents, said: “It is a real shame that travellers are facing such disruption at this time of year, especially as it is the first Christmas when people should be able to travel freely after the pandemic.
“Anyone travelling over the next few days will have spent a lot of money to have a Christmas break abroad and these strikes will impact their plans.”
Thousands of UK ambulance workers and paramedics go on strike — video
Thousands of UK ambulance workers and paramedics go on strike
Meanwhile, motorists are being warned to prepare for long queues as millions of people embark on journeys to spend Christmas with friends and family.
The Automobile Association said Friday would be the busiest day on the roads this week, with an estimated 16.9 million journeys being made across the UK.
Flooding on the M25 caused a 10-mile queue on motorway, which circles London, because lanes were closed between junction 11 (Woking) and junction 12 (the M3 motorway) while standing water was cleared, National Highways said.
Many drivers are battling a band of heavy rain which is moving north from southern England and Wales to southern Scotland and Northern Ireland throughout the day.
Junction 4 of the M20 westbound in Kent was also closed for several hours on Friday morning, following a serious crash on Thursday.
The AA reported “severe congestion” on several other motorway stretches on Friday, and said industrial action on the railways has added to the number of vehicles on the roads.
The locations with “severe congestion” included the M1 around Luton, the M4 and M5 near Bristol, the M5 north of Birmingham, the M60 west of Manchester and the M8 near Glasgow, according to the breakdown rescue company.
AA president Edmund King said: “Friday and Saturday will be the busiest on the roads with some 17 million trips each day.
“Then we're expecting Christmas Day to be quieter with shorter local journeys.”
“On Boxing Day traffic will pick up again with approximately 15 million trips as people head out to see friends and family.”
Transport analytics company Inrix expects journey times to be around 14 per cent longer compared with the same period last year.
National Highways said almost 98 per cent of England’s motorways and major A-roads will be fully open until the end of January 2, because it has completed and halted roadworks.
“We are advising those heading out in their cars to be prepared for some congestion, especially on popular routes heading out of London,” said Jack Cousens, AA head of roads policy.
“The rail strikes have convinced more people to travel by car this year, and while hundreds of miles of roadworks have been removed to ease the pain, it might not be enough to keep the queues away.”
RAC spokesman Rod Dennis said there would be “two frantic days of travelling just before Christmas”.
“With pre-pandemic levels of travellers hitting the road this holiday, drivers must be prepared for delays, especially in and around major cities,” said Inrix transport analyst Bob Pishue.
