Much like American's earlier lawsuit against Google, the airline alleges that Yahoo unlawfully allows other companies to use the words "American Airlines" to trigger paid search ads.
The airline's case against Google ended with a settlement, but the details are confidential so it's hard to know whether American got what it was looking for out of that lawsuit.
But Google has previously prevailed in court when companies have tried to argue that their trademarks shouldn't be used to trigger ads. Four years ago, Google won at trial in a similar lawsuit brought by insurance company Geico. There, federal district court judge Leonie Brinkema in Alexandria, Va. found that Geico hadn't proven that consumers were confused when they typed "Geico" into the query box and paid search ads appeared for Geico rivals on the results page. (Google and Geico reached a settlement about another portion of the case.) Yahoo also was a defendant in that case, but Yahoo and Geico settled before trial.
In another instance, computer repair shop Rescuecom also sued Google and lost. The trial judge in that case never reached the question of whether people were confused by ads for Rescuecom rivals, ruling simply that arranging for a trademarked term to trigger a search ads isn't a "use in commerce." The 2nd Circuit Court of Appeals is currently considering an appeal in that case, but even if that court reverses and orders a trial, Rescuecom won't necessarily prevail.
Of course, American Airlines has one major advantage in its lawsuit against Yahoo: the airline filed suit in its backyard, Fort Worth, Texas. That's the same courthouse where it sued Google, and the lawsuit has been assigned to the same judge, John McBryde, who presided over the now-settled case.