is expected to announce Tuesday that it will eliminate its booking fees on airline tickets sold through May 31, matching a move last week by competitor

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, which is a unit of Sabre Holdings Corp., and Orbitz Worldwide Inc. typically charge $6.99 to $11.99 to book an airline ticket. The fees are usually folded in with government taxes and fees.

Those companies also generate revenue off hotel bookings, car rentals, travel insurance and advertising on the Web sites.