Currently, no two F-117 Nighthawk Stealth Fighters are the same. As the production line went along, new techniques for applying the RAM (Radar Absorbent Materials) were developed. The first planes were produced by gluing sheets of RAM onto the airframe, but more than halfway through the run a new spray-on technique was developed (and later changed more than once). Several different treatments have been used for the wing edges, cockpit rim, access panels, and other areas. As the material degraded or was damaged over time, several different repair techniques were used. Access panels were another variable, as some aircraft had to have the RAM scraped off to open them while others had treatments that provided easier (and less destructive) access. Stealth works in various ways, and stealth aircraft use a combination of techniques. The basic concept, however, is to make the stealth coating one-fourth of a radar wavelength thick. In this way, some of the enemy radar beam is reflected by the surface of the RAM and more by the metal under the RAM later. Because this second element travels a half of a wavelength farther than the first element, it exactly cancels out the radar wave.--Stephen V Cole