The EU rule, which will apply to UK holidaymakers, will cover companies including easyJet, Ryanair, Wizz Air and TUI

The European Union is planning a change in the rules on carry-on bags on flights, which would cover planes flying between the UK and countries including Spain, Portugal, Greece, France and Italy. At the minute, some airlines charge passengers for each item they want to take aboard.

Different airlines have different rules – meaning the size of the bag you can take aboard and how much it will cost you – is different each time. The new EU rule would set a specific size of bag you would be allowed to take on flights operated by companies like easyJet, Ryanair and Wizz Air.

And the rule would stipulate that the take-on bag would be free, the airline would not be able to charge you extra to take a bag aboard the plane.

The rule would change the confusion that see people being charged extra when they get to the airport for bags deemed too big, or too heavy. And people being charged for a bag by one airline but allowed to take it without additional fees by another.

EU transport ministers this week proposed standardised sizing for free underseat baggage on EU airlines. It will become law if it is accepted by the European Parliament. The new rule would mean passengers are guaranteed one free personal item, measuring up to 40x30x15cm (including wheels and handles) – or which could reasonably fit under a plane seat.

The rules would apply to EU-based airlines, including when they are carrying passengers from a non-EU country like the UK to an EU country and vice-versa.

11 years ago, an EU court ruled that hand baggage should not be subject to an additional fee so long as it is a reasonable size. But the ruling did not define ‘reasonable’.

Currently, Ryanair allows a free carry-on bag of 40x20x25cm, while easyJet’s rules for a free bag are 45x36x20 cm, including wheels and handles. The new rule would cover under-seat bags, but does not currently mention bags you put in overhead lockers.

In November, five airlines in Spain were fined £150million for ‘abusive practices’, including charging for hand luggage. Spain’s Consumer Rights Ministry said it planned to ban charging extra for carry-on luggage.

Ryanair told the BBC it fully complied with EU law. A spokesman said: “If airlines were forced to include additional carry-on bags as part of the basic fare, it would reduce choice and drive up air fares for all passengers, which would harm consumers.”

Industry group Airlines For Europe said charging different amounts depending on baggage “allows passengers to choose the exact services that best suits their needs”.

Travel consumer expert Jane Hawkes, told the BBC: “A one-size-fits-all kind of approach would make it a lot simpler for passengers.”