The walkout is the latest act in a string of disputes between the London hub and the Unite union after staff walked out over pay conditions in the build up to Easter and over the coronation weekend.

But despite the strikes, Heathrow chief executive John Holland-Kaye assured passengers "operations will continue to run smoothly". "Passengers should not be concerned about strike action by Unite over the half term getaway," he said.

"The 15 days of strike action over the Easter peak and coronation weekends have had no impact on the smooth running of the airport, and passengers have not noticed any difference from the normal great service they expect at Heathrow."

Holland-Kaye said the airport made a "generous" 10% pay offer early on, to make sure colleagues got a "substantial" increase when "they needed it most".

However, research by Unite claimed since 2017, in real terms, the average remuneration of HAL workers has fallen by 24%. Unite also discovered Heathrow security officers are paid less than workers at other major airports in London and the South East.

Unite general secretary Sharon Graham said: "These figures underline all that is wrong with Heathrow airport - mega payouts to the shareholders while the workers who generate the dividends are on poverty pay."

Which? Travel editor Rory Boland said: "While it is positive to see Heathrow has put contingency plans in place to minimise disruption during the forthcoming strike action, those with flights booked over half term will no doubt still have concerns that their trips could be impacted.

"It’s essential that airlines and airports work together to keep travellers updated during this period of industrial action, and fulfil their legal obligations to passengers in the event of cancellations or delays."

He reminded travellers to ensure they have travel insurance from the date they book their trip and to always check the policy carefully, to ensure it covers all the eventualities.