Military pilots are trained to interpret their instruments and sensors in very specific ways that relate to combat information. Those instruments and sensors are, in turn, designed to collect and present readings in very specific ways. Both the human pilots and the devices they use are imperfect and subject to both systematic and random errors. Much of the data in the purported sighting incidents falls into the area where both instrument and pilot are outside their designed regime. In those places, things with perfectly normal explanations are subject to mis-interpretation. One example I'm aware of is claims of a some object rolling and turning in what appear to physically extreme, if not impossible, ways, turns. out to be explained by noting that the artifacts like diffraction spikes follow the changes in the direction of the light source relative to the observer and instrument, as the device slews through its range of motion.