Airfix Spitfire Mk 21, a work in progress. Image source: Airfix gallery, user HawkerTempest5.
It will probably not surprise readers of this site to learn that I had a collection of model aeroplanes as a boy. It was small but diverse: a Mustang, a Kaydet, a Lancaster, a F-16 (and some ships too, the USS Pennsylvania and the Santa Maria) ... maybe some others I can't remember now. (They did not long survive the arrival of a baby brother.) However, I lacked the patience and the dexterity to be very good at making them. Probably the low point was the Lancaster. I didn't have the right colour paints, so it ended up being painted in the highly distinctive but ... erm ... somewhat unhistorical camouflage scheme of the Desert Air Force. Not only that, but I laid it on so thickly that if it were scaled up to full-size, I doubt it would ever have gotten off the ground under the weight of all that paint!
Airfix started making scale models in the 1950s (its first aeroplane was a 1/72 scale Spitfire in 1955). The first plastic scale models were the Frog Penguins, starting with a Gloster Gladiator in 1936. But it seems that the basic idea goes back a few years earlier, when the components were made from solid wood (so-called "solid scale" models), with some metal and acetate. In fact, an article at CollectAir suggests that the honour for originating the concept should go to the Air League of the British Empire:
A Junior Air League section was formed by A.J. Holladay, called the "Skybird League" in 1933 and the decision was made to market commercial solid-scale model kits of current model airplanes in 1:72 scale. Many "Skybird" members who crafted models from these kits and drawings later became RAF pilots such as Neville Duke. This was a civilian commercial endeavour, nevertheless it was the progenitor of the government recognition model program for the British and for the U.S., both of which would come belatedly.
I haven't been able to verify this yet, but it makes sense. The Air League had always been interested in promoting an airminded youth: as early as April 1909, only two months after it was founded, the Aerial League of the British Empire (as it was then known) staged a balloon flight and leaflet-dropping competition with the Boy Scouts, at Battersea Gasworks. Under J. A. Chamier in the 1930s, the Air League lobbied the government to set up an air cadet scheme, which bore fruit in the shape of the Air Defence Cadet Corps, formed in 1938 (today's Air Cadets Organisation is a direct descendent).
So swearing over the placement of fiddly decals and the smudging of acetate canopies with glue goes back a long way. If Airfix disappears, there will be other companies to carry on the tradition (the industry is particularly strong in Japan), but it will still be a sad day.