The United States formally handed Rhein-Main Air Base over to the German government Monday, ending a 60-year stay during which the sprawling field was a hub of activity for American forces facing Soviet bloc troops and Mideast tensions. Gen. Robert Foglesong, commander of the U.S. Air Force in Europe, called it "a grand old base with a lot of history," but said moving operations to other bases in Germany was necessary to save money.Instead of the constant landings and takeoffs of C-130s, F-16 Fighting Falcons and the gargantuan C-17s ferrying tons of supplies and thousands of troops worldwide, Rhein-Main Air Base has gone quiet, nearly devoid of activity as it prepares to shut down. The handover, based on a 1999 U.S.-German agreement, will take until the end of the year. Fraport AG, which operates the adjacent Frankfurt International Airport, plans to use the additional space as it prepares to house a new maintenance and supply facility for the new Airbus super-jumbo A380, the world's largest passenger jet. Construction began last month on the new hangar, part of a $124 million effort to get ready for the plane.