The Saunders-Roe SR.N5 (or Warden class) was a medium-sized hovercraft which first flew in 1964. It has the distinction of being the first production-built hovercraft in the world. A total of 14 SR.N5s were constructed. While Sauders-Roe had developed and produced the type, an additional seven vehicles were also manufactured by Bell Aerosystems under licence in the United States, designated as the Bell SK-5. A number of SK-5s were operated by the US military, this includes a number which became Patrol Air Cushion Vehicles (PACV), and saw action during the Vietnam War. The SR.N5 was subsequently developed into a "stretched" variant, which was designated as the SR.N6; this model had a much expanded payload capacity and went on to be produced in greater numbers than the SR.N5.