Caveat emptor is the watchword when travelers compare prices and journey times, and the beguiling claims and obfuscations of airlines. Many travelers have learned to their cost that the price of an air ticket they have purchased online can just about double when it comes to the final amount charged. Extra charges, such as fuel surcharges, and airport taxes, often add up to more than the price of the ticket. (A friend flew from Frankfurt to London with Lufthansa: The fare was ?11 - plus ?99 "taxes.")

While some airlines, including British Airways and Virgin Atlantic, include taxes, fees and charges throughout the booking process, others, especially low-cost carriers, do not, said the Air Transport Users Council, a British monitoring group.

The group's chairwoman, Tina Tietjen, said: "There remains a risk that passengers are not aware that airlines charge different taxes and charges on a route and therefore may not look at other Web sites to compare fares. They have a further problem in that they must compare prices between those airlines that quote inclusive prices and those that don't."

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