The new U.S. commander of the Pacific Fleet has joined a seven-hour surveillance flight over the South China Sea on board one of America's newest spy planes.

The U.S. Pacific Fleet said Sunday that Adm. Scott Swift joined the surveillance mission on board a P-8A Poseidon plane on Saturday to witness the aircraft's full range of capabilities.

The Navy has acquired and plans to purchase more of the multi-mission aircraft, which can be used for anti-submarine warfare and surveillance missions, to replace its aging P-3 Orion fleet.

U.S. Navy Capt. Charlie Brown said Swift "was pleased with the capabilities of the Poseidon."

Swift assured U.S. allies Friday that American forces are ready to respond to any contingency in the South China Sea, where territorial disputes have set off uncertainties.