Hainan is currently the home of the PLAN Hainan Submarine Base, an underground facility capable of supporting nuclear ballistic missile submarines.[44] In March 2009, the USNS Impeccable, an ocean surveillance ship of the U.S. Navy, was on several occasions approached by Chinese ships and aircraft while operating 75 miles (121 km) south of Hainan; in actions Pentagon officials characterized as "aggressive" and "harassment."[45][46] In August 2014, the U.S. protested when a Chinese Shenyang J-11BH came within 10 meters (30 ft) of a patrolling Boeing P-8 Poseidon aircraft and performed aerobatic maneuvers including a barrel roll.[47] In May 2016, the U.S. protested when two Chinese Shenyang J-11BH aircraft reportedly came within 15 meters (50 ft) of a U.S. EP-3 on "a routine" patrol approximately 50 miles (80 km) east of Hainan Island; China responded by demanding an end to U.S. surveillance near China.[48]