Extra charges tallied onto advertised flight costs have become a bugbear of jumbo sized proportions for airline passengers.
Booking fees, baggage charges and a host of optional service fares are now common industry practice. Baggage fees were last year worth more than $3.3 billion to the American aviation industry, while fees for reservation changes netted U.S. airlines $2.38 billion in 2011, according to the Bureau of Transportation Statistics.
As a result, ticket prices that initially appear good value rapidly rise once an array of extra expenses are factored in to the equation.
"Additional fees for things like baggage allowance and seat selection can be above and beyond what it costs the airline (to offer these services)," says Chris Gray, deputy editor of UK-based consumer magazine Which? Travel.
"These are often sprung on customers at the end of a long booking process," catching them out unfairly, he says.
John Heimlich, chief economist of U.S. aviation industry body, Airlines for America, holds a different view, however.
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He believes airlines have no option but to employ ancillary charges. This enables them to streamline their costs and offer customers greater value for money in an increasingly competitive marketplace, he says.
Heimlich also rebuffs claims that airlines are trying to catch out unsuspecting fliers by surreptitiously adding extra charges to airline tickets.
"Unlike a lot of other services, the airline industry was one of the last to unbundle its services," he says.
"The consumer is now getting a choice of what they pay for. It's in nobody's interest for airlines to charge customers for services (like in flight meals or entertainment) that they don't use."
So how fair are the extra airline charges that passengers love to hate?
Most budget airlines now charge customers for items of non carry-on luggage. With the vast majority of established airline industry players, one item of baggage (up to a certain weight) and one carry on is permitted before a fee is incurred.
Two U.S. airlines, Spirit and Allegiant, have recently begun to charge passengers for carry-on cases.
According to Gray, these kinds of policies are immensely frustrating for consumers who have more than one bag or an item of luggage deemed too big for the plane cabin.
On top of that "many people have told us they distrust the airlines' weighing systems," he adds.
John Heimlich retorts that these fees give customers more choice and could actually save them money. If customers weren't given the option to pay for baggage requirements separately then this extra cost would automatically be added to the price of the ticket, he says.
See also: Truth in airline fees is best option
Seat selection charges
One of the more recent additional cost options to come to the fore has seen some airlines charge a premium to reserve seats on their aircraft.
In the United States, Delta, American Airlines, and low-cost carriers U.S. Airways, Frontier, Spirit and Allegiant have implemented charges for "preferred seating."
In Europe, budget carrier Ryanair began offering specific seats at an extra cost earlier this year. Its low-cost rival Easyjet has also started to experiment with the practice.
"(This is) something many airlines used to allow you to request for free," says Gray. "So incurring charges for these now is irritating, especially for families who are told they have to pay to select seats so they can sit together."
According to Heimlich, however, these charges again provide the customer with more choice in what they do and do not pay for.