Its design allowed for its construction and maintenance tasks to be carried out without specialised tools, making it suitable for use in countries that had not yet become highly industrialised.

Although never used as a fighter by the Royal Air Force (RAF), the Gnat T.1 jet trainer variant was adopted and operated for some time.

In the United Kingdom, the Gnat became well known due to its prominent use as the display aircraft of the RAF's Red Arrows aerobatic team.

[3][4] Almost immediately upon joining the firm, Petter conducted a study into the economics behind modern fighter manufacturing, and concluded that many combat aircraft entailed far too great a cost in terms of man-hours and material to be readily mass-produced during a major conflict.

[4] While the British Air Staff emphasised quality over quantity, the economics involved in the anticipated vast wartime production of many of the RAF's aircraft of the time, such as the Hawker Hunter and the Gloster Javelin interceptors, were viewed as questionable.

[4] Petter examined the prospects for producing a more affordable but capable "light fighter", including a survey of available modern engines to power the type.

[4] Having identified suitable powerplant arrangements along with methods of making multiple key design aspects, such as the manufacturing of the fuselage and wings, more affordable, Folland promptly commenced work upon this lightweight fighter concept, financing the project using existing company funds.

[3] Development of the Gnat and the specifics of its design were heavily influenced by the issuing of Operational Requirement OR.303, which sought a capable lightweight fighter aircraft.

[3][5] Petter believed that a compact and simplified fighter would offer the advantages of low purchase and operational costs, and that the Gnat should be capable of being manufactured both cheaply and easily.

[3] The emergence of new lightweight turbojet engines, several of which were well advanced in their own development process, also enabled the envisioned light fighter concept to be realised.

[1] The Gnat was initially intended to be powered by a Bristol BE-22 Saturn turbojet engine, capable of generating 3,800 lbf (16.9 kN 1,724 kgp) of thrust.

However, development of the Saturn was cancelled; in its place, the more capable but not immediately available Bristol Orpheus turbojet engine was adopted instead.

[3] While using a different powerplant from later-built prototypes and production aircraft, the demonstrator still used a nearly identical airframe along with similar onboard systems so that these could be proved in advance of the Gnat itself being built.

On 20 September 1955, the Midge was destroyed in a crash, which had possibly been due to human error by a pilot from a potential overseas purchaser.

[7] The Midge, partly due to its nature as a private venture, had only a short lifespan, however had served as a proof-of-concept demonstrator for the subsequent aircraft.

[12] However, the Gnat was evaluated in 1958 by the RAF as a replacement for the de Havilland Venom, as well as other light aircraft such as the BAC Jet Provost.

Although RAF interest in the possibilities for using the Gnat as a fighter had waned, Folland identified a potential use for the type as a trainer aircraft.

A more powerful variant of the Orpheus engine was also used, while the length of the forward fuselage area was increased, and the tail surfaces were enlarged.

Following the take over of Folland by Hawker Siddeley Aviation (becoming the Hamble division), further orders for 30, 20 and 41 trainers were placed between February 1960 and March 1962, receiving the designation Gnat T Mk.

[17] This model was to be capable of supersonic speeds and was intended to be made available in both single-seat and twin-seat configurations, enabling its use in the trainer and interceptor role.

According to aviation author Derek Wood, the Fo.147: "would have provided a first-class flying test-bed for variable geometry theories...even a VG conversion of the standard Gnat Mk 2 fighter would have been an invaluable research tool".

[19] However, neither the Fo.147 nor its successor, the Fo.148, would be developed to the prototype stage; the RAF showed little interest in the need for a variable-geometry trainer, although it intended to procure the General Dynamics F-111K strike aircraft.

[20] The cockpit offered many features expected in standard fighter aircraft: full pressurisation, climate control, and an ejection seat.

[4] According to Folland, the Gnat offered advantages over conventional fighter aircraft in terms of cost, man-hours, handling, serviceability, and portability.

[4] Similarly, the layout and construction techniques used allow the airframe to be rapidly disassembled into its major subsections, without the use of cranes or ladders; the Gnat was vastly easier to service than most other aircraft.

All Gnats were grounded for half a year on 26 August 1958 after the destruction of GN-102 due to a technical design error in its hydraulic system, and the aircraft soon became the subject of severe criticism.

[26][27] During the initial phase of the 1965 war, an IAF Gnat, piloted by Squadron Leader Brij Pal Singh Sikand, landed at an abandoned Pakistani airstrip at Pasrur and was captured by the PAF.

[28][29] Sikand — who had a complete electrical failure on his Gnat while he got separated from the IAF flight to fight a Sabre — had to make an emergency landing at the PAF field at Pasrur.

To address these failings, the IAF issued a requirement for an improved "Gnat II" in 1972, at first specifying that the new version was to be optimised as an interceptor but then expanding the specification to include ground-attack.