The nation's largest airline reservation system may soon sell information about some passengers' destinations, hotel accommodations and other travel arrangements under a marketing proposal that could raise new questions about privacy. Sabre Group executives said they plan to use data warehouses--sophisticated computer technology that vastly increases the speed of information processing--in a variety of promotions. Although the company declined to provide specifics, it acknowledged its plans could involve the sale of personal travel information about passengers who give consent. Potential customers of such information could include airlines, car-rental companies and other firms that want to market to travelers. But those plans have raised questions about privacy, in part because Sabre collects information that could allow marketers or others to track an individual. "This brings to light the fact that airlines in particular have a ton of information. They have where you're traveling to, who you're traveling with, the car you drive, what you're eating," said Deirdre Mulligan, staff counsel at the Center for Democracy and Technology. "This is personal information." Sabre officials said they will not sell information without approval from travelers.