Airlines are on alert for an order from Heathrow that could require them to stop selling tickets over the busy Easter holiday period.
Strikes are likely to cause major disruption at Europe’s busiest airport as Unite members walk out for 10 days from the end of the month in a dispute over pay.
Talks failed to reach an agreement, the airport announced on Friday. Heathrow said it had offered a 10 pay increase pay increase, and further enhancements based on feedback from workers.
The strike means there will be fewer security officers available to search passengers, crew, catering and cargo. heathrow said it had contingency plans to deal with the walkout.
A Heathrow spokesperson said: "These strikes are completely avoidable and not supported by the majority of Unite members at Heathrow.
"We are taking action to minimise the impact on those who have already booked, including asking airlines to open flexible booking policies and to put a hold on the sale of new tickets on strike days.
"We urge Unite to do the right thing. Passengers do not deserve unnecessary disruption over Easter and colleagues deserve the 10 per cent pay increase that's on the table."
Airlines said they are in touch with Heathrow over the possible effect of the strike.
A representative from Etihad Airways said passengers booked on flights from London Heathrow, or those transiting the airport to onward flights between Friday March 3 and Sunday April 9 are being advised of the industrial action planned by security workers that will affect all airlines using the airport.
The action does not effect Etihad customers “ending their journey at Heathrow”, the representative said.
The representative added: “Heathrow Airport has contingency plans in place and is asking passengers to turn up for their flights as normal. However, the strike is set to cause delays for guests passing through security on departure from London, as well as those transferring to other flights on arrival.
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“Flights will depart to London Heathrow from Abu Dhabi International Airport as normal.
“Etihad is working closely with the airport authority in London to understand the impact and avoid disruption to our guests. More information regarding these strikes will be communicated via our website and social media accounts when available, and customers are advised to ensure they check for the latest information online before they travel.”
Other airlines bracing for the effect of the strikes said they were reviewing the data with Heathrow before making decisions on potential measures, such as stopping ticket sales in the affected window.
“Our priority is to ensure that our Heathrow customers can complete their travel plans as smoothly as possible, if the proposed Unite industrial action by Terminal 5 security guards goes ahead,” said a spokesperson for Virgin Atlantic.
“We are working with Heathrow to understand the potential impact of the strike on customers at our home in Terminal 3 and what measures could be required.”