Jet2 is warning customers travelling to and from Portugal of potential disruption over the bank holiday weekend.
The airline said there could be delays getting through security at Portuguese airports due to ongoing strike action.
The next strikes are due to take place at Lisbon airport from Saturday 27 May to Monday 29 May.
Strikes at Porto, Faro and Madeira are planned for Monday 29 May.
The industrial action will continue at all four airports on various dates throughout June.
In a message on its website, Jet2 said the strikes could lead to longer queues at border control on Monday.
The airline advised passengers flying home from Portugal on Monday to leave enough time to get through security ‘by checking in and clearing security as quickly as possible’.
“If you have already checked in for your flight, please allow extra time at the airport for the security procedures. Our customer helpers will be on hand to make your journey as smooth as possible,” it added.
Customers travelling on a Jet2holiday will be advised of their transfer pick up time, it added.