Hawker Siddeley Harrier and better equipped for air defence, to replace their AV-8S Harriers; this investigation did not progress to a purchase. The last first-generation Harriers were retired by Thailand in 2006. Hawker Siddeley Harrier The Hawker Siddeley Harrier, developed in the 1960s, is the first of the Harrier Jump Jet series of aircraft. It was the first operational close-support and reconnaissance fighter aircraft with vertical/short takeoff and landing (V/STOL) capabilities and the only truly successful V/STOL design of the many that arose in that era. The Harrier was developed directly from the Hawker Siddeley Kestrel prototype aircraft, following the cancellation of a
Hawker Siddeley P.1127 after the P.1154's selection over the Dassault Mirage IIIV. Following the termination of the P.1154, the RAF then began studying a straightforward upgrade of the Kestrel as a production aircraft; accordingly, it issued Requirement ASR 384, which sought a V/STOL ground attack jet, known as the "P.1127 (RAF)". In late 1965, the RAF placed an order for six pre-production P.1127 (RAF) aircraft. On 31 August 1966, the first of these P.1127 (RAF) aircraft made its maiden flight. In early 1967, an order for 60 production aircraft was formally received by Hawker Aviation; at this time the aircraft received the "Harrier