They were Folland Gnats, an early British jet fighter that first flew in
1954 (as the Midge).  It was designed as a private venture by Folland, to
demonstrate that a lightweight fighter was a practical alternative to the
trend towards heavier and more complex aircraft.  It entered RAF service
only as a trainer (Gnat T.1), but both the fighter and trainer versions
were built under licence by HAL in India, as the Ajeet (unconquerable);
India, Finland, and Yugoslavia also imported British-built Gnat fighters
(as well as a reconnaissance version for Finland).  The trainer version
equipped the RAF's Red Arrows aerobatic team before the arrival of the
Hawk.  The Ajeet remains in service with India.  The Gnats seen in _Hot
Shots_ were all privately owned.

Vital statistics (Gnat F.1):  length 9.06 m, span 6.75 m, empty weight 2200
kg, max TO weight 4030 kg, max speed 1150 km/h, max range 1900 km; power
plant:  one 20.10 kN Bristol Orpheus 701 turbojet; armament:  two 30mm Aden
cannon (115 rounds each), four hardpoints, max external load 454 kg.