Priceline.com Inc, Travelocity.com Inc and Preview Travel Inc plan to form a marketing alliance to take advantage of their combined user base of 20 million travelers. The companies say they will give each other seamless access to air products and services on their web sites and through their affiliates. Under certain conditions, each company will generate incremental revenue when they facilitate the sale of another company’s products. When the alliance is up and running, members of Preview Travel and Travelocity.com will be able to name their own prices through the Priceline.com service. In return, Priceline.com’s customers will have access to the retail fares displayed on Travelocity.com and Preview Travel. The plans are detailed in a memorandum of understanding, and the partners hope to finalize the alliance as soon as possible. This alliance is what web travel customers have wanted for a long time, argued Priceline.com’s president and CEO Daniel Schulman. In the past, if you wanted the best travel deal it meant surfing from site to site spending precious time. This alliance will make it possible to go to our own sites or many of the nation’s largest search engines, ISPs and online services to buy travel products at the price you want. This convenience is what the internet was intended to deliver. Now it will.