Before the advent of satellites, aircraft were routinely used for intelligence gathering on friends and foes alike. This practice even involved aeroplanes engaged in scheduled air services. The reason was obvious: by flying on a regular service, pilots could gain geographical and positional awareness that they could later use when flying military aircraft in the event of war. This paper discusses how these military-related aspects shaped the formal and informal regulation of international civilian air traffic between 1919 and 1989. In doing so, the paper places the main emphasis on Czechoslovakia, which was one of the leading aviation countries in both the inter-war period and the Cold War era.
