Based on the US Air Force requirement for a new, highly manoeuvrable light-weight fighter, in 1971 General Dynamics started to develop the F-16. By the mid 1970s the NATO countries Belgium, Denmark, Holland and Norway enquired after the fighter to reequip their forces. The first production F-16A flew in 1987. From 1980 onwards these air and ground attack fighters were known by the nickname "Fighting Falcon". Over 4000 examples of this machine with a speed of over 2.0 Mach were built. The Falcon excelled in the field of avionics and was unequalled for manoeuvrability. Since its introduction, this most important present day fighter has been continually upgraded. (It is in active service with 18 air forces).