Google Inc.'s newest push into online travel has begun to roil the industry, the latest example of the company extending its market power into increasinglydiverse aspects of economic life.

Competitors say Google is abusing its power in Web search to gain sway over the $110 billion online travel business.

Starting in December, Google began placing its new flight-search service atop general search results so that its own results appear prominently above links to major middlemen such as Expedia Inc., Orbitz Worldwide Inc. and Priceline.com Inc.

Google searches such as 'NY to LA' now yield a Google-powered interactive chart of the cheapest airfares between the two cities. Google's flight tool links exclusively to the airlines' websites.

Pushed further down on the screen are links to top travel websites, which rely on Google for 10% to 20% of their traffic, according to web analytics firm Compete Inc.

Just how Google ranks and displays searches has become a key question for modern commerce, where Google stands as a gatekeeper for buying decisions. Once content to simply produce search results, the 13-year-old company is increasingly getting into the guts of these markets, too, offering everything from online music to local coupons to mobile phones.

In many ways, Google is still learning how to balance the conflicting demands of being both search-arbiter and market competitor.

Google's tool is still imperfect. It only searches domestic flights. Google said it is working to add international ones, and ultimately, it aims to trigger the tool with searches such as 'flights to somewhere sunny for under $500 in January.'