In an about-face for an airline that has shunned travel search engines, American Airlines formed a partnership with San Mateo, Calif.-based Mobissimo, one of the new meta search companies.

An American spokesman would not provide details of the agreement but said American had determined that Mobissimos business model represents a low-cost form of distribution.

In public presentations, Mobissimo has described three options for participants: CPC (cost per click), in which the supplier pays Mobissimo for each referral to its Web site; cost per action (CPA), in which the supplier pays Mobissimo for each booking, and cost per thousand (CPM), in which the supplier pays Mobissimo for every 1,000 impressions.

It is not clear what moved American to change its mind about the search engine model. Until now, it has ferociously defended its Web site from screen scrapers and other forms of search.

Its flights appear in SideSteps search results only when they appear on Orbitz, which has an agreement with SideStep.

In 2003, American sued FareChase, a screenscraper that marketed itself to corporations and travel management companies, charging that it enabled unauthorized parties to redistribute Americans Web fares.

American said it tries to protect its Web site from scrapers through the terms of its AA.com user agreement, which prohibits the use of automated devices to scrape the Web site. Ultimately, the two companies settled the case. American agreed to license FareChases MarketView software, which enabled suppliers to benchmark air fare performance and price competitiveness. American also granted FareChase special access to AA.com that allowed FareChase to search the site, but only travel agencies enrolled in Americans now-defunct EveryFare program were able to book the airlines Web fares through FareChase.

FareChase was bought last year by Yahoo, which has been transforming itself into a leisure travel search vehicle. AgentWare has begun serving several of FareChases former clients. In other news on the search engine front:

This week, Yahoo FareChase unveiled the beta version of its hotel search product. It searches a number of proprietary hotel sites and online vendors including lastminutetravel.com, onetravel.com and placestostay.com. It does not search all sites for all locations, however; for example, in some smaller markets it does not search the Holiday Inn or Holiday Inn Express sites even when the properties are in the market.

America Online launched a beta version of its new search engine, powered by Kayak and dubbed PinpointTravel.com. The site has a strange quirk: It often offers only one itinerary that matches the request even when the customer requests a JFK-LAX roundtrip and a long list of flights to or from alternate airports, some that are 100 miles away from the preferred airport.

Kayak also is powering travel searches for U.S.-originating requests on LonelyPlanet.com.