The U.S. always had been under the threat of hostile radar systems and the ground-to-air missiles at the so-called "cold war" era. Therefore the stealth technology has attracted the attention of the U.S. Air Force and developed by the Lockheed, the project team was called "Skunk Works".
The concept of stealth technology was to defeat the radar signal given off by the hostile defense systems. F-117A Night hawk was the first stealth fighter proven for the evidence of stealth technology. This aircraft has been covered up in secrecy for a long time. However, the public was finally allowed to see the photograph published by the Department of Defense in 1988. The F-117A looks so strange compared with conventional fighters. For example, it has an angular fuselage composed of black surfaces with radar-absorbent paint to minimize any radar detection, no curved wings and V-tail with good direction control.