UK airlines have collected overweight baggage charges amounting to £553m from air travellers over the last five years, a sum equal to the cost of two Boeing 747 aircraft.

The figure was reached by travel agent Florida4Less, which compiled passenger data from the Civil Aviation Authority with research into the average excess baggage charge by UK airlines.

“Many airlines have very complicated rules for it, and they aren’t always easy to find out. What’s more, they can change at short notice.”

After that, the company carried out its own study into the proportion of travellers who have been caught out at check-in.

It found that nearly 46% of UK air passengers have been charged for overweight baggage at least once since January 2013.

With 100.7 million people having travelled from the UK during that period, it is estimated that 46.3 million travellers have underestimated the weight of their luggage.

The company found that the average fee charged is £11.93 per kilogram, which means the total bill is at least £553m when assuming each bag was just one kilo overweight.

Florida4Lessco-founder and director Jon Moulding said: “It really is a staggering figure. While paying an excess baggage charge is an inconvenience at the time, you often don’t realise how these fines can add up.

“On the other hand, it isn’t that surprising that 46% of people have been charged for overweight baggage at least once in five years. Many airlines have very complicated rules for it, and they aren’t always easy to find out. What’s more, they can change at short notice.”

To help passengers plan beforehand, Florida4Less has published a guide to baggage charges for airlines that commonly fly from UK airports.