British Defense Secretary John Hutton announced on Wednesday that the United Kingdom will purchase three F-35B Lightning II operational test aircraft, signaling the U.K.’s commitment to the upcoming Operational Test and Evaluation phase of the Joint Strike Fighter program. Hutton made the announcement during a visit to Washington, D.C.

The F-35B is the first aircraft to combine stealth with short takeoff/ vertical landing (STOVL) capability and supersonic speed. It will be the next-generation fighter for the Royal Navy and Royal Air Force, and will be flown from the two new Queen Elizabeth Class aircraft carriers. The U.K. plans to bring 138 F-35s to the fleet.

The U.K. is investing $2 billion in the F-35′s development – the largest contribution among the program’s eight partner nations. More than 100 British companies are involved in the program, including BAE Systems, which produces the aircraft’s aft fuselage and tails; Rolls-Royce developer and manufacturer of the shaft-driven lift fan and other propulsion components for the F-35B STOVL variant; and Martin Baker, maker of the jet’s ejection seats.