The online travel vendors face intense competition from Web sites that search for airline prices and refer shoppers directly to airline sites, which typically don't charge booking fees.

Travelocity also is expected to launch a long-term price guarantee of sorts on vacation packages, promising to refund a price difference, from $10 to $500, if a different Travelocity customer buys the same package for a cheaper price at a later date. The "PriceGuardian" program is similar to an offering competitor makes on airline tickets called "Price Assurance."

Expedia Inc., Travelocity, and Orbitz typically charge $6.99 to $11.99 to book an airline ticket. The fees are usually folded in with government taxes and fees.

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