The Duke of Cambridge has qualified as an operational search and rescue captain, Clarence House has said.
William - known as Flight Lieutenant Wales in the military - has previously only co-piloted RAF Sea King helicopters but will now be able to command operations.
He completed two days of ground and air-based tests to achieve the qualification, following two years of flying experience.
William joined C Flight, 22 Squadron at RAF Valley in Anglesey in September 2010.
Officer Commanding 22 Squadron, Wing Commander Mark Dunlop, said: "Flt Lt Wales demonstrated the required standards needed for the award of Operation Captaincy.
"Due to the nature of search and rescue operations, the required standards are always set at a very high level. Operational Captaincy carries the overarching responsibility for the safety of the aircraft, its crew and any casualties."
William, whose rank remains Flight Lieutenant despite his new qualification, finished his tests on May 29.
The mock rescue scenarios saw him take part in an airborne search for a yacht, a search for two missing kayakers, a search for people in water and extinguishing a simulated fire on a large survey vessel.