Back in the 1950s, when the Air Training Corps was part of RAF Home Command, units were assigned to numbered Groups of the command rather than ATC Regions as at present. In 1955 the Gliding Schools ( not squadrons in those days) were renumbered in blocks of ten with the first two digits being the group number. ATC units in Scotland were assigned to 66 (Scottish) Group, Home Command and so No.1 Gliding School (GS) at Turnhouse was renumbered 661, 2 and 5 GS at Edzell became 662 and 4 GS at Abbotsinch became 663. In the same way schools in 61 Group became 61x, 62 Group 62x and so on. The numbers have been retained ever since although the unit titles have changed from Gliding School to Volunteer Gliding School and most recently to Volunteer Gliding Squadron.
664 VGS was formed more recently ( 1986 ) [
664 VGS :: History :: ] and the reason for the choice of number is unknown, it might have been appropriate to re-use 671 as that been the previous Gliding School in Northern Ireland.
There is a comprehensive history of the ATC gliding organisation up to 1983 in the article
"Cadets with Wings", by the late Ray Sturtivant, in
Aviation News, Volume 11, No 24 - dated 22 April -5 May 1983.
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Philip Morten