The boss of Heathrow has pledged that strikes by security guards at Heathrow are unlikely to cause flight cancellations.
More than 2,000 members of the Unite union will walk out for 31 days from June 24 in a dispute over pay.
For the first time, security officers based at Terminal 3 will join their colleagues from Terminal 5 and campus security who have already taken industrial action.
Heathrow chief executive John Holland-Kaye said that having kept running through earlier strikes over Easter, the airport is well-prepared.
“We have delivered excellent service to passengers, with no cancellations, over eight days of strikes on the busiest days in May, and do not anticipate cancellations as a result of strikes during the summer holiday getaway.”
Last week, Mr Holland-Kaye urged Unite to put the airport’s latest proposal of a 10% pay increase and £1,150 lump sum to a vote of its members.
He claimed: “We know that most of our colleagues would accept the offer that we have on the table.”