The much-reduced budgets for peace-time air forces dictated a cautious approach to innovation; yet in these two decades aeroplane design underwent one of the biggest transformations in its history. Rotary engines were discarded in favour of their more efficient radial and in-line counterparts; metal gradually replaced wood and fabric as the principal structural material, bringing smooth-skinned machines with semimonocoque bodies; and the monoplane, first ushered in by Blériot in the first decade of the century, at last came into its own. The speeds and the armament of military aeroplanes likewise increased in proportion.
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