Forty years ago this month, the Paris Air Show was abuzz over the debut of the Boeing 747, the largest-ever passenger aircraft. But even as spectators lined up for a first look at the jumbo jet, Europe was preparing to challenge the Americans' dominance in the skies. Within months, European aerospace companies created Airbus Industrie, a consortium that would establish itself as a formidable rival to Boeing (BA). Today, Airbus is neck-and-neck with Boeing in a global duopoly. Besides competing in the passenger jet sector, the two companies are vying for a multibillion-dollar U.S. Air Force tanker aircraft contract. They're also the focal point of a trade dispute between the U.S. and the European Union over alleged government subsidies to both jetmakers. Click on for a look at the 40-year history of their transatlantic rivalry.