Heathrow travellers are being warned they could face disruption as security officers begin a new series of strikes today.

Staff who are members of the Unite union will walk out from 4-6 May, with other strikes planned for 9-10 May and 25-27 May.

Heathrow bosses are advising people to check their flight status before going to the airport.

Passengers will only be able to bring two carry-on items through security on strike days – and Heathrow is reminding customers that handbags and laptop bags count as a piece of hand luggage.

Checked luggage allowance is not affected.

The airport is also asking travellers to arrive no earlier than two hours before short-haul flights and three hours for long-haul flights.

“We anticipate that the airport will be busy during this period, and additional ‘Here to Help’ teams are available to assist passengers,” Heathrow said.

About 1,400 security staff at the London airport are Unite members and the union claims the walk-out will cause “May mayhem”.

Heathrow security staff staged a similar series of strikes at Easter.

The airport said operations continued “smoothly” during that period – and that it’s confident the new industrial action won’t disrupt people using Heathrow in the build up to the coronation.

Unite regional co-ordinating officer Wayne King said the strikes were “a direct result of Heathrow’s stubborn refusal to make an offer that meets our members’ expectations”.

“Our members have been crystal clear they are seeking a substantial permanent increase in pay.

“A small one off lump sum payment will not alleviate the financial pressures our members are facing on a daily basis,” said Mr King.

An average security officer at Heathrow gets paid £30,000, according to Unite, which said there had been a 24% real-terms pay cut since 2017.

Heathrow said last month that it had offered workers a 10% increase and a one-off £1,150 since January – but claimed the union failed to put the revised offer to members.

Edinburgh Airport could also face disruption this summer, with about 275 workers to be balloted by Unite over going on strike.

It said its members had rejected an inferior pay offer to one made to staff at Gatwick; 11% plus a £1,000 one-off payment, compared with 12% and £1,500 at the Sussex airport.