It found that currently some flights cost as little as £7.49 with Ryanair, yet if you want to reserve a seat you will have to stump up as much as £15. Rival airline Jet2 charges £25 if passengers want to select which seat they will sit in, yet it currently has flights on offer for just £24.

It’s worth noting that seat reservation costs can vary significantly between airlines. While some, like Lufthansa, offer the facility free on some flights, others charge far more. Costs can even vary depending on flights from the same airline and some fees are based on your ticket-type and where you want to sit.

The table below breaks down some of the different charges for reserving a seat from major airlines:

Source: Kayak

John-Lee Saez, travel expert at KAYAK, said that if you check in at the desk then you may be able to secure the seat you want free of charge simply by being polite.

“But in many cases, if you are checking in automatically, or with an airline where the format is ‘first come, first served’ when you get on board, the only way to guarantee is to pay,” he added.

“Our advice is to do your research up front. Some airlines charge as little as nothing whilst others can cost as much as £70 extra for priority seating. Sometimes the comfort is worth the cash, but don’t get caught up with unnecessary charges if you’re happy to sit next to whoever on the flight.”

Earlier this year Ryanair was criticised by passengers over its seat allocation policy, with allegations that the firm was deliberately seating passengers flying under the same booking reference number separately, in a bid to force them to pay in order to sit together.

Boss Michael O’Leary denied this and had little sympathy for passengers, saying: “If you’ve made the choice, stop whinging afterwards.”