For almost half a century, the jumbo jet has meant one plane: Boeing's 747. The gigantic airliner, which first flew in 1969 and started carrying passengers in 1970, is an icon of the sky, ferrying hundreds of passengers between continents regularly since its introduction. But the venerable sky giant's reign may soon be at an end. In September, Boeing expects to cut production from one 747 a month to one made every two months. If demand continues to fall, the company says in a regulatory filing, "it is reasonably possible that we could decide to end production of the 747."