Hawker Siddeley Harrier as VTOL and STOL manoeuvres (where the traditional lift and control surfaces are useless) requiring skills and technical knowledge usually associated with helicopters. Most services demand great aptitude and extensive training for Harrier pilots, as well as experience in piloting both types of aircraft. Trainee pilots are often drawn from highly experienced and skilled helicopter pilots. In addition to normal flight controls, the Harrier has a lever for controlling the direction of the four vectoring nozzles. It is viewed by senior RAF officers as a significant design success, that to enable and control the aircraft's vertical flight required only a
Hawker Siddeley Harrier fuel consumption. The AV-8A's abilities in air-to-air combat were tested by the Marine Corps by conducting mock dogfights with McDonnell Douglas F-4 Phantom IIs; these exercises trained pilots to use the vectoring-in-forward-flight (VIFF) capability to outmanoeuvre their opponents and showed that the Harriers could act as effective air-to-air fighters at close range. The success of Harrier operations countered scepticism of V/STOL aircraft, which had been judged to be expensive failures in the past. Marine Corps officers became convinced of the military advantages of the Harrier and pursued extensive development of the aircraft. Starting in 1979, the USMC began upgrading their