A fresh round of strikes by security guards at Heathrow airport is expected to be announced this week.
Members of Unite are in a long-running dispute about pay which has led to previous industrial action.
On Friday, Unite announced there would be 33 days of strikes throughout the summer, although its official announcement was later retracted.
An airport spokesperson confirmed Heathrow is yet to receive formal notification about any action.
The Heathrow spokesperson added: “Passengers can rest assured that we will do everything we can to minimise strike disruption so they can enjoy their hard-earned summer holidays.
“Unite has already tried and failed to disrupt the airport with unnecessary strikes on some of our busiest days and we continue to build our plans to protect journeys during any future action.
“The simple fact remains that the majority of colleagues do not support Unite’s strikes.
“There is a two-year inflation-beating pay rise ready for colleagues, if only Unite would allow them to have a say. We will continue talks with Unite about resolving this issue.”
Last month, Unite warned that the pay dispute at Heathrow airport is set to “escalate” as about 600 more security officers had voted to join the dispute.
Security staff members of the union at Terminal 3 recorded an 85% vote for strike action.
They are set to join 1,400 colleagues at Terminal 5 and airport campus security, who are taking industrial action.
Elsewhere, Unite confirmed that its members employed by OCS Group UK Limited based at Glasgow airport will be balloted on strike action.
About 70 Unite members previously rejected an offer by 96% which would take basic pay to £10.90 per hour.
The ballot will open June 6 and close a fortnight later on June 20.
If the ballot is successful, Unite members could begin strike action in early July.
More: Half-term strike ‘will not affect flights’, Heathrow insists