That fare you see may not be the fare you get -- here's why

Yet something similar sometimes happens when shopping for airfares at third-party travel websites such as Orbitz, Expedia and Travelocity, according to several recent studies from Consumer Reports WebWatch, a project of the nonprofit Consumers Union based in Yonkers, N.Y.

"What we see is shoppers are being advertised a price that's not available," said William J. McGee, consultant to Consumer Reports WebWatch. "There is no other place in the market where that's acceptable."

The phenomenon is called "fare jumping," and it occurs when an airfare changes price (usually an increase) during the online purchase process. According to a WebWatch study released last fall, airfares on Orbitz increased 21% of the time and decreased 5% of the time. Orbitz declined to comment for this story.

The problem was less pronounced at Orbitz's largest competitors, the study showed. Expedia showed an increase 5% of the time and a decrease 2%; Travelocity fares increased 1% of the time and decreased 1%.

Fares can change quickly because the lowest fares are sold in limited quantities. The fare you see one moment may be bought out the next by another shopper, said Kari Swartz, a spokeswoman for Expedia.

"If a confirmed shopper is further along in the search, then that seat's no longer available for us to sell," Swartz said.

Current technology doesn't allow checking every possible airfare combination and holding every one of those fares while the customer decides whether to purchase the ticket.

"Online agencies connect, for the most part, to the airlines through an intermediary," said Jared Blank, an analyst for New York-based Online Travel Review, which publishes travel industry updates. The most efficient way for the intermediary to perform is to store fare data and update them regularly. When a consumer says, "Yes, sell me that ticket," the online agencies query the airline sites directly to confirm real-time availability.

"There is a time lag," Blank said. "The [intermediary] is not passing on information to you in real time."

To address the problem, the third-party agencies have added warnings when a fare changes during the booking process. That's important because the difference can be as little as $5 or $10, which consumers may miss.