Publisher Summary The development of airborne magnetometer is considered one of the major advances in geophysical exploration. In context to aeromagnetic surveying, this chapter summarizes the instrumentation, development, and use of the airborne magnetometer. The most useful type of airborne magnetometer consists of a detecting mechanism that is self-oriented with respect to the Earth's field, the electronic oscillators and amplifiers required for its operation, and the equipment used to measure and record its output—the variations of the earth's total magnetic field. The heart of the airborne magnetometer is the fluxgate or saturable inductor. This consists of a core of easily saturable ferromagnetic material of high permeability with an external winding to which an alternating voltage is applied that produces a magnetic field h that drives the core cyclically through saturation. It is observed that the airborne magnetometers produce a continuous record of the total magnetic field along the flight path of the aircraft, but the obtained data cannot be plotted and used unless it is constantly correlated with the position of the plane in space.