The importance of model aircraft in the development of both powered aircraft and gliders especially, is very significant. Indeed, it can be argued that the two went hand-in-hand and the tradition still exists today to a crucial extent. The obvious example being models used for testing in wind tunnels.
It is hard to determine when models were first used? In the UK Sir George Cayley, now recognised as the pioneer of flight, certainly used models to prove his theories.The steam powered model built by William S Henson and John Stringfellow in the loft of the Lace Mill in Chard, Somerset, was of a size equivalent to several light aircraft designs.
GETTING BACK TO BASICS
The model aircraft can be as basic as the paper dart fashioned by school children, typically, from a sheet of A4 paper. And indeed, by tweeking the trailing edges to provide better 'trim' control in pitch, roll and yaw the basic elements can quickly be learnt, and much better results achieved.
In my youth at least, very basic 'gliders' could be purchased, pressed out from a sheet of balsawood. The prefered trim method as I remember, being to add a blob of plasticine to the nose of the model. From memory I don't think they flew any better than the paper-dart design.
MORE ADVANCED MODELS
Certainly from the early twentieth century, serious model makers were perfecting highly capable designs, but, please correct me if I am wrong, the entire scene was changed forever when radio control came along fairly shortly after WW2. This meant that all models, gliders and powered types, could be very accurately flown, right down to landing on a suitable strip of land anywhere.
SHEER INGENUITY & EXPERTISE
The expertise that model makers have shown in the decades following the introduction of radio control, and the imagination and ingenuity shown, is quite extraordinary.
For example, models can be, and have been, used by film makers to recreate flying scenes in many movies - going back to the 1930s at least. Today of course, the models are so good, it is almost impossible to differentiate them from the real thing. In this way, quite fantastic scenes can be created - without reverting to the far more expensive option of CGI, (Computer Generated Imagery).
ANOTHER RECENT DEVELOPMENT
In recent years there has emerged the existence of radio controlled 'model' drones. Mostly used as short range 'toys' they are, nevertheless, now sometimes presenting a hazard in the hands of mostly stupid youngsters to aviation ranging from the military to civil airliners.
I don't think this has ever been a problem with mainstream model aircraft flyers?
The use of Drones for professional purposes is another subject entirely, and has been a revolution especially for makers of documentary films, surveys and a host of other purposes. In June 2020 I was kindly contacted by Mr Steve Gerrard who pointed out that since the 30th November 2019, drones weighing over 250g need a CAA licence. This costs £9 per annum and comes with a sticker giving the licence number. Flying a drone without one is illegal.