Heathrow Airport is set to face severe disruption as staff announce several walkouts.
The London hub has confirmed there will be strikes at the end of April and for much of May.
The Unite union has warned that planes will likely be "delayed, disrupted and grounded".
The long weekend walkout is part of a slew of strikes to be held by different departments at the UK's biggest airport over the next few weeks.
Border Force officers are set to strike from 29 April to 2 May
The Public and Commercial Services trade union (PCS), which represents Border Force officials, says more than 300 of its members will strike on 29-30 April and 1-2 May.
Taking place at terminals 2, 3, 4 and 5 of the airport, the strike will affect arrivals rather than departures.
But why is it happening?
The union says around 250 Border Force staff are set to lose their jobs at passport control under new roster plans.
"Our members are angry and disappointed at being forced out of their job," says PCS general secretary Fran Heathcote.
"While not everyone will be affected, the changes will disproportionately hit those who are disabled or have caring responsibilities.”
She hit out at the Home Office, saying it "should be doing all it can to retain experienced, trained staff - not lose them by introducing an unworkable new roster system."
In response, the Home Office said it was "disappointed" with the union's decision but assured that it is still "open to discussing a resolution".
In a statement it defended the alterations, saying: "The changes we are implementing will bring the working arrangements for Border Force Heathrow staff in line with the way staff work at other ports, provide them with more certainty on working patterns, and improve the service to the travelling public.
"Keeping our borders secure remains our top priority and we have robust plans in place to minimise any potential disruption."
Refuelling workers will strike over the early spring bank holiday from 4 to 6 May
Some 50 refuellers working at Heathrow are set to strike on 4, 5 and 6 May, causing severe disruption for passengers travelling over the bank holiday.
Workers union Unite says their employer, aviation fuel firm AFS, has been imposing cuts to the terms and conditions of new staff recruited since January 2024. That includes offering them reduced pension and sickness benefits.
Airlines including Emirates, Virgin Atlantic and Tap Air Portugal will be affected, although Heathrow is hopeful disruption can be kept to a minimum.
The airport says it is working contingencies with AFS to avoid any chaos, insisting it has "robust" measures planned for the walkout dates.
Almost 800 staff in various departments set to walkout from 7 to 13 May
The most significant - and largest - strike will take place for an entire week in the second week of May.
Unite members from passenger services, trolley operations, campus security, firefighters and airside operations will walk out from Tuesday 7 May all the way through to Monday 13 May.
This particular strike was announced as Unite says the airport will outsource the work of passenger services, trolley operations and campus security by 1 June, in an apparent "cost-cutting exercise". Heathrow says the changes would save it some €47 million.
"This cost reduction will lead to a substantial reduction in the number of workers, which raises serious security concerns, given the safety critical nature of much of the work undertaken," Unite said in a statement.
Firefighters and airside operation members are said to be striking in solidarity because they fear they "may be next in line" to have their work outsourced, according to the union.
Unite has warned the strike action "will inevitably cause widespread disruption across the airport, leading to delays and disruption".
"Heathrow Airport's actions are deplorable, it is raking in massive profits for the bosses while trying to squeeze every last penny out of its workforce,” Unite general secretary Sharon Graham said in a statement.
"Unite is fully focused on defending its members jobs, pay and conditions and our members at Heathrow will receive the union's unrelenting support during this dispute."
In response, a spokesperson for Heathrow said: "We are reorganising our operations to deliver better results for our customers. There are no job losses as a result of these changes and we continue to discuss with Unite the implementation of these changes for the small number of colleagues impacted.”
Criticising the strike action, Heathrow also said passengers shouldn’t worry unduly about disruption: "Unite's threats of potential industrial action are unnecessary, and customers can be reassured that we will keep the airport operating smoothly, just like we have in the past."
While Heathrow says the strikes are just ‘threats’, it’s likely at least some of them will go ahead in the upcoming weeks.