CHICAGO -- In the airline industry's latest aggressive thrust into cyberspace, three more U.S. carriers have joined Priceline.com, giving a big boost to the name-your-own-price Internet ticket service.
The endorsement Wednesday by United Airlines, American Airlines and US Airways means that nearly all major domestic airlines now sell seats through the service. The move also doubles the number of seats Priceline can sell.
It paid immediate dividends on Wall Street for the fast-growing online retailer. Stock in Stamford, Conn.-based Priceline soared $8.25 Wednesday to $77 a share, a 12 percent rise, by midafternoon on the Nasdaq Stock Market.
The agreement gives travelers more reason to buy tickets online and provides airlines with a proven way to peddle unsold airline seats at the last minute.
It also deals another blow to travel agents, reeling from the latest round of airline commission cuts and new competition from travel Web sites.
Most airlines now sell tickets on their own sites, and last week United, Delta, Continental Airlines and Northwest announced plans for a joint site.
Priceline's three new carriers -- Nos. 1, 2 and 6 in the country -- join Delta, Continental, Northwest, Trans World Airways and America West on Priceline. Among major carriers, Southwest Airlines is still not participating.
Priceline's new partners previously had been reluctant to sell tickets there, particularly American, which feared stirring competition with Travelocity.com, the travel Web site controlled by its parent AMR Corp. All three airlines sell tickets at their own Web sites.
But results apparently persuaded them; Priceline says its weekly sales of airline tickets have increased to more than 50,000 a week, up 1,000 percent from January.