Strikes at UK airports and ports are set to impact travellers in February, March and April.
Half-term holidaymakers could face disruption when returning home between 17-20 February as UK Border Force go on strike.
A further walkout is planned for 15 March, which is set to involve around 100,000 civil service workers, including Border Force staff at airports. More than 2,000 flights could be impacted.
Heathrow is bracing for yet more chaos next month, with members of UK union Unite balloting for strike action over the Easter break in April.
Where are Border Force strikes taking place?
The Public and Commercial Services union has announced that Border Force staff at the ports of Dover, Calais, Coquelles and Dunkirk will be striking on 17, 18,19 and 20 February.
The dispute over pay, jobs and working conditions will see around 1,000 members of the Public and Commercial Services (PCS) at four UK ports walk out until 7am on 20 February.
"The strikes... in the Border Force will impact on people returning from their holidays during the half term period," said Serwotka.
The Home Office has warned passengers to be prepared for disruption, keep up with the latest advice from travel operators and check how the strike could affect them.
A further strike has been called for 15 March. This is part of a wider civil service worker strike and could involve Border Force workers at ports and airports, including London Heathrow, Gatwick, Stansted, Manchester and Edinburgh.
PCS general secretary Mark Serwotka said: "The blame for these strikes lies firmly at the feet of ministers who are refusing to put any money on the table".
Heathrow strikes over Easter could double down on airport chaos
Next month, Heathrow Airport could face further disruption over the Easter holidays if members of Unite vote to strike over pay and conditions.
“Heathrow Airport is guilty of gross hypocrisy, it is paying telephone number salaries to its chief executive and senior managers, but the workers who make the company a success are on poverty wages," says Unite general secretary Sharon Graham.
The ballot, open to over 3,000 workers, will close on 17 March.
How have Border Force strikes affected travel so far?
Last summer, holidaymakers faced hours-long delays at the Port of Dover because of slow border checks caused by staff shortages and new Brexit controls.
Since Britain left the European Union in 2020, UK travellers face stricter border checks when travelling to the continent. At Dover, they are performed on the English side of the channel by French staff.
Serwotka added that, while "untrained military personnel" has been brought in to replace striking workers in the UK, the government won't be able to do this in France.
On 1 February, Border Force officers took part in a series of coordinated strikes involving teachers, civil servants and train drivers. Around half a million workers walked out.
During the Christmas Border Force strikes, passport checks at Heathrow, Gatwick, Manchester, Glasgow, Cardiff and Birmingham were affected. Border Force staff at the port of Newhaven, East Sussex, were also included in the strikes.
In response, the government drafted more than 800 military personnel and civil servants to staff entry gates.
Heathrow was challenged with recruiting and training up to 25,000 security-cleared staff before the festive period, a task the airport described as “a huge logistical challenge”. Passengers who were not eligible to use eGates faced longer wait times at Border Control.
At Manchester Airport, 200 new security staff are being recruited, but won't start work until April 2023.
More than 10,000 flights carrying up to 2 million passengers arrived at the affected airports during the strike period, according to aviation analytics company Cirium.
How might the government reduce disruption?
"Military personnel, civil servants and volunteers from across government are being trained to support Border Force at airports and ports across the UK in the event of potential strike action," the UK government said in a statement.
"Border Force are ready to deploy resources to meet critical demand and support the flow of travellers and goods through the border, however, those entering the UK should be prepared for potential disruption."
But the head of the armed forces said during previous strikes that they should not be thought of as "spare capacity" for striking workers.
"We're busy and we're doing lots of things on behalf of the nation - we've got to focus on our primary role," chief of defence staff Admiral Sir Tony Radakin told the Sunday Telegraph.
Is there a danger of problems with passport checks?
Steve Dann has insisted that safety and security at borders will be "non-negotiable" during strike action.
However, unions have warned that military personnel are not properly qualified to carry out these jobs. PCS said that Border Force members "are specialists in their fields and can't be replaced by people with just days of training."
Why are border force officials striking?
The strike is part of a larger coordinated action by thousands of civil servants. 100,000 PCS members in 214 government departments and other public bodies voted to take action
Members are demanding a 10 per cent pay rise, citing eye-watering inflation of 10.6 per cent.
Mark Serwotka, the PCS general secretary, said that the strike would cause "significant disruption" - but added that the cost of living crisis has left workers "desperate" with no choice but to strike.
"We have no option but to take industrial action because our members are using food banks and not able to switch on the heating right now," he said.
"The government can stop these strikes tomorrow if it puts money on the table."