Booking rewards miles can be confusing if you don’t know which fees to look for. (iStock)

If you’ve tried to book an international flight using your rewards miles recently, you might have noticed something strange.

Two round-trip flights on the same route that require the same amount of miles can turn out to have starkly different price tags at checkout, with the gap amounting to hundreds of dollars.

That can be confusing, if not utterly disappointing, for people who have finally racked up enough miles to book a round-trip flight to Europe or Asia or any other far-off destination.

The difference is due to a fee that many travelers may not fully understand: the fuel surcharge that some airlines include on international flights, sometimes referring to it as a carrier fee.

Take a search on the American Airlines website for a round-trip flight from New York City to London taking off Oct. 5 and returning a week later. One flight turning up in the search had a total cost of 60,000 miles plus $171 in taxes and fees. But a similar flight that is chartered by American’s partner airline British Airways would cost more than four times as much for the same dates and the same amount of miles: $729.

After clicking through to get a detailed breakdown of the taxes and fees being charged, travelers can see that the difference is due to a carrier fee. As the image below shows, the flight chartered by British Airways included $211 in taxes and $518 in “carrier-imposed fees.” The flight through American Airlines charged $171 in taxes and zero carrier-imposed fees.

A flight chartered by British Airways, through a partnership with American Airlines includes $518 in “carrier-imposed fees” for travelers booking with rewards miles. A nearly identical flight chartered directly by American charges zero carrier-imposed fees. (

The charge, which is usually baked into the total airfare, is not typically an issue for travelers until they are redeeming rewards miles. That’s because rewards miles apply only to the base fare of the flight, not the taxes and fees. For example, both of the flights mentioned above were priced at $1,119 for people not using their miles. It’s not until travelers try to book them with rewards miles that the different prices appear.

The fuel surcharge, or carrier charge, became more popular several years ago when oil prices were increasing and airlines added them to help offset the rising cost of fuel. But to make things more confusing, it turns out the fee hasn’t always been pegged to the cost of fuel, analysts and consumer advocates say. Some airlines are still including the charge as part of their total airfare, even as those fuel costs have fallen dramatically, and they aren’t required to disclose what goes into deciding the fee.

A spokeswoman for British Airways said that the charge does not apply to flights within Europe. “We always quote fares inclusive of all taxes, fees and charges, which apply to all our tickets, including redemption tickets,” she wrote in a statement, adding that the company does not comment on the details of its fares.

The surcharges don’t necessarily make flights more expensive overall. At the end of the day, airfare is determined mostly by supply and demand, even during periods like now, when fuel costs are dropping, says Darryl Genovesi, an equity analyst covering U.S. airlines for UBS.

Still, people booking flights with rewards miles should be aware of which airlines tack on the surcharges and on which flights so that they can avoid the fee, says Charlie Leocha, president of Travelers United, a travel advocacy group.

“Just by being careful about what flights you pick you can save” hundreds of dollars, Leocha says.

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