The creation of what Winston Churchill named the 'Iron Curtain' along the borders between Western and Eastern Europe in the late 1940s made conventional espionage extremely difficult. This forced the Western powers to fall back upon their large fleets of transport aircraft and bombers for intelligence-gathering work. The range of aerial spying activities were extensive, from classic photoreconnaissance, the insertion of agents deep within enemy territory (HUMINT), through to electronic intelligence (ELINT) - subdivided into communications intelligence (COMINT), signals intelligence (SIGINT) and telemetry intelligence (TELINT) - to the monitoring of nuclear tests. Always at the forefront of such activities, the Central Intelligence Agency (CIA) of the USA clandestinely developed a large organization, operating dozens of - often heavily - modified aircraft for all of these purposes. Their activities reached frantic proportions especially during the late 1940s, when the Agency became
