Billboard boasts fly over routes to Shanghai: United, American duke it out near O'Hare

It seems United Airlines, newly emerged from bankruptcy, justcan't resist yanking the chains of its longtime archrival AmericanAirlines, the world's largest carrier.

First, there was the unusually pointed campaign United waged inprint and on television last year to remind travelers of its roomyEconomy Plus section in the carrier's coach cabins. Hardlycoincidentally, that ad campaign was launched just as Americandecided to do away with its competitive "More Room Throughout Coach"seating arrangement in economy that offered all passengers seatedthere more leg space.

Now United is engaged in a dueling billboards battle at O'HareAirport suggesting its archrival is …