American Airlines has filed a federal lawsuit over Google's keyword advertising, claiming it infringes on the airline's trademarks, reports The Register.

It says that when you type in one of the airline's trademarked terms, such as Aadvantage -- the name of its frequent-flier program -- links to the airline's Web site appear, but also rival sites under "sponsored links," according to an Associated Press. It claims third-party businesses should not be allowed to piggyback their ads on the airline's trademarked keywords.

Among the suit's many allegations, the airline says Google is actively shopping ads to competitors that piggyback on American's trademarks.

Google responded that previous lawsuits on the matter have found its advertising practices are legal.