INTRODUCTION The Story of Airborne Electromagnetics After the end of World War II, the reconstruction of war-ravaged economies fueled a great demand for natural resources. The emerging Cold War caused explorationists to seek secure supplies in countries geographically and politically close to the United States. With vast areas that were then little explored, Canada was one obvious choice. These circumstances provided a great incentive to develop geophysical methods whereby a sparsely populated country, where the climate is often harsh and frigid for part of the year, could be scanned quickly and effectively for deposits of strategic base metals, such as copper, lead, zinc, and nickel. Airborne magnetometer systems that were developed from early war-time prototypes used in submarine detection became widely used in mineral exploration in Canada. However, it soon became obvious that the magnetic information was of more value indirectly in aiding geologic reconnaissance than it was directly in ore exploration. The abundance of magnetic bodies in deformed metamorphic terrains with base metal potential made it difficult to select specific targets for more detailed exploration on the ground. An alternative or additional technique was, therefore, required to carry out prospecting from the air.