During the past several years the electromagnetics laboratory at NASA Langley Research Center has focused on the Aging Aircraft Program. A major goal of this program has been the development of easy to use yet highly accurate inspection methods for the detection of flaws in airframe fuselage structures. A major breakthrough in this research came with the discovery of the Self-Nulling Probe Effect in November of 1992 [1]. It was clear that the unambiguous flaw signature of the probe could be developed into a low cost and easy to use fatigue crack detection device. Work toward this goal proceeded quickly, and a prototype hand held crack detector was introduced by mid 1993 [2]. As research into the precise flaw detection mechanism of the probe began to provide a deeper insight into the device [3–4], more sophisticated uses of the probe were conceived [5–6]. In particular, the Rotating Probe Method for the Detection of Fatigue Cracks under Airframe Rivets was beginning to be developed and tested by the end of 1993 [6], less than 1 year after the original discovery of the Self-Nulling Probe Effect.