The U.S. Air Force on Friday handed over the keys to Rhein-Main Air Base to the operator of Frankfurt International Airport in a final act of closure for the base, which for 60 years hosted American forces.

The 120 buildings on the base are to be bulldozed to make way for a third terminal for Frankfurt's sprawling civilian airport — continental Europe's busiest. It officially becomes German property on Saturday.

The ceremony, at which Brig. Gen. Mike Snodgrass gave the keys of the base's buildings and main gate to Manfred Schoelch of airport operator Fraport AG, followed Rhein-Main's formal closing in October.

"It's bittersweet — after 60 years of partnership, to see it come to an end," said Capt. Jonathan Friedman, a U.S. Air Force spokesman.

The 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 earlier this year for a hangar.

Rhein-Main was once a hub of activity for American forces facing Soviet bloc forces and tensions in the Middle East. It saw a steady stream of planes fly supplies to West Berliners in the late 1940s during the Soviet blockade of the city.