Composite aircraft construction
I note earlier in the thread someone cited a glass fibre glider as the pioneer of the present day composite structure and another cited the Mosquito.
You need to go much further back to 1919 to the Loughhead S-1. The procedure and technique was further developed for use in the Lockheed Vega series which began in 1926. The 1937 Clark/Fairchild Duramold process was a further refinement as was the similar Vidal process used for the fuselage of the wartime Canadian-built Anson Mk.V.
Not sure when this type of construction was first used for the mainplane.
M-63A3