“All passengers with flights on these dates may alter their voyage or request that their ticket be reimbursed, without additional costs, through the usual sales channels," SATA said in a message sent to passengers.

In the same message, the company stated which flights are included in the skeleton service assured by unions on the strike days.

In the case of SATA Internacional, which links the archipelago to mainland Portugal and beyond, flights on 1 June between Lisbon and Santa Maria and Horta are guaranteed. On 2 June, flights between Lisboa and Horta are guaranteed.

As for SATA Air Açores, which covers air transport within the region, flights are available for all nine islands on both days.

A company official advised that passengers “check whether their flights are or not assured in the skeleton service and, if they are not, they can change their flight to another day, before or after the strike period [or] we will allow reimbursement."

Some flights may also take place that are not included in the skeleton service, the official stressed.

Next month's planned strike follows one on 1 and 2 May.