Expedia Inc., the large online travel vendor, just eliminated its booking fee for airline tickets sold between now and May 31, according to a report in the Wall Street Journal. The move reflects the intense competition among travel Web sites, and could well be the start of a trend.

Online travel sites like Expedia, Travelocity and Orbitz typically charge $6.99 to $11.99 to book an airline ticket–you pay for their service. The fees are fairly well hidden because the sites fold them in with government taxes and fees. Those companies also make money off hotel bookings, car rentals, travel insurance, advertising and whatever else they can gin up, the Wall Street Journal reported.

But savvy shoppers know they can use the booking sites to shop across many airlines, and then typically book the trip directly from the airline and save the online agency fee. What's more, the online booking sites face lots of competition from search-only sites like Kayak.com that compare lots of different offers and then send you to whatever Web site you want–most likely an airline's booking site, but sometimes a vendor like Orbitz or others. The search-site gets a referral fee; the traveler gets the cheapest price.