Ryanair is to end its practice of allowing passengers to take a 10kg piece of hand luggage for free, with non-priority passengers being charged between €6 and €10 to do so from November.
From 1 November, non-priority passengers can only bring one free "small personal bag" on board.
However, under the new rules, if a non-priority passenger wants to bring a medium-sized suitcase of up to 10kg, they will now have to pay.
They can pay between €6 and €8 to take it on board and put it in the overhead locker or pay between €6 and €10 to check it in.
Only priority customers can bring two free carry-on bags.
The airline said it was making the change as planes were being delayed as passengers brought too much hand luggage.
Rivals easyJet, Wizz and Norwegian AirShuttle currently all allow a medium-sized piece of hand luggage for free on short-haul flights.
Ryanair said it does not expect to make additional revenue as checking in a 10kg bag under the new system is significantly cheaper than the current cost of checking in a bag.
It also said it was increasing the size allowed for all bags.
The new policy will go live at boarding gates from 1 November and for all bookings made from 1 September.
The ballot is due to take place after an agreement was reached between Ryanair and pilots' union Fórsa.