The United Kingdom is one of the top export customers of the Lockheed Martin F-35 fifth-generation fighter. The British F-35B acquisition has faced a rocky road, with the number planned seeming to change constantly. They are vital for the British ability to maintain an expeditionary fighting capability. Separately, a British F-35B had a near-miss with a drone flying 36x above the legal height. The UK is also the only country to soley purchase the naval F-35B S/VTOL variant of the fighter for both its navy and air force.