Unite said nearly 800 members will take part in a week of action beginning at 12.01am on Tuesday 7 May and ending at 11.59pm on Monday 13 May.

The dispute centres on plans to outsource staff who assist passengers with connections, plus employees with trolley collection roles and security personnel who check workers and their vehicles. Deals have already been agreed with three outside companies.

A Heathrow spokesperson said the airport was reorganising its operations "to deliver better results" for travellers, and insisted no jobs would be lost as a result.

Unite said the action would be backed by firefighters and airside operations staff who fear they “may be next in line”. 

The union claims outsourcing will save the airport £40 million and lead to job losses. It added the decision to outsource campus security guards was “a complete reversal of the agreement hammered out with Unite last summer, when as part of the deal to end industrial action, the company agreed to begin the process to bring all security guard roles in-house”.

The union said the airport had made £701 million in 2023, “above what it was making prior to the pandemic” – although this figure drops to £38 million when including exceptional items. Unite also accused Heathrow chiefs of ignoring consultation procedures by announcing the changes from 1 June.

Unite general secretary Sharon Graham said: “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.”

The airport also faces industrial action by Unite members at AFS Ltd, an airline refuelling company, over 4-6 May. However, it is thought numbers involved in both disputes are not enough to disrupt day to day running of the airport.

Heathrow said: “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.” 

“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.”