Stealth aircraft are designed to avoid detection using a variety of technologies that reduce reflection/emission of radar, infrared, visible light, radio frequency (RF) spectrum, and audio, collectively known as stealth technology. The F-117 Nighthawk was the first operational aircraft explicitly designed around stealth technology. Other examples of stealth aircraft include the B-2 Spirit, the F-22 Raptor, the F-35 Lightning II, the Chengdu J-20, the Shenyang J-35, and the Sukhoi Su-57. While no aircraft is completely invisible to radar, stealth aircraft make it more difficult for conventional radar and radar-guided weapons to detect or track the aircraft effectively. Stealth is a combination of passive low observable (LO) features and active emitters. LO features encompass the geometric stealth shaping of the aircraft, often using a lambda wing or trapezoidal wing, and radiation-absorbent material. Active emitters consist of low-probability-of-intercept radars, radios and laser designators. These are typically combined with operational measures to minimize the aircraft's radar cross-section (RCS), since common hard turn maneuvers or opening bomb bay doors can more than double a stealthy aircraft's radar return. Stealth aircraft are sometimes complemented by reduced heat, sound, and other emissions. Countermeasures to stealth include infrared search and track systems to detect even reduced heat emissions, long wavelength radars, which counter stealth shaping and material focused on shorter wavelength radar, or radar setups with multiple emitters to counter stealth shaping. Full-size stealth combat aircraft demonstrators have been flown by the United States (in 1977), Russia (in 2000) and China (in 2011). As of 2025, the only crewed stealth aircraft in service are the Northrop Grumman B-2 Spirit (1997), the Lockheed Martin F-22 Raptor (2005), the Lockheed Martin F-35 Lightning II (2015), the Chengdu J-20 (2017), the Sukhoi Su-57 (2020), and the Shenyang J-35 (2025) a number of other countries developing their own designs. In-development aircraft include fighters such as the US F-47 and China's J-36, as well as strategic bombers, China's H-20 and Russia's PAK DA. There are also various aircraft with reduced detectability, either unintentionally or as a secondary feature. Stealth aircraft first saw combat when the F-117 was used in the 1989 United States invasion of Panama. Since then U.S., UK, and Israeli stealth aircraft have seen combat, primarily in the Middle East, while the Russian Su-57 has seen combat in the Russian invasion of Ukraine. In March 2026, during the 2026 Iran war, a stealth fighter first shot down a crewed fighter in combat, when an Israeli F-35I "Adir" downed an Iranian Yak-130 fighter jet over Tehran. As of 2026, there has been one confirmed shootdown of a stealth aircraft, during the 1999 NATO bombing of Yugoslavia, of a USAF F-117 by a Serbian Isayev S-125 'Neva-M' missile brigade commanded by Colonel Zoltán Dani, while a second incident damaged an F-117. Russia and allegedly China studied the relatively intact wreckage.
Design principles Besides all the usual demands of flight, the design of a stealth or low-observability aircraft aims to reduce radar and infrared (thermal) detection, including:
Reduce thermal infra-red emission from the engine and its exhaust wake Reduce radar reflection back to a hostile receiver by shaping the airframe Reduce radar reflections from the airframe by the use of radar-absorbent materials (RAM) or radar-transparent materials such as plastics. Reduce radar detection from exposed internal surfaces such as the cockpit, weapons bay and engine intake ducting. The distance at which a target can be detected for a given radar configuration varies with the fourth root of its radar cross-section (RCS). Therefore, in order to cut the detection distance to one tenth, the RCS should be reduced by a factor of 10,000. Size, shape, material composition, radar frequency, polarization, and direction of observation all factor into the amount of energy reflected by a target when illuminated by radar. Rotorcraft introduce a particular design challenge, due not only to their multiple wing surfaces and articulated joints, but also to the constantly-changing relationship of these to the main airframe surfaces. The Boeing–Sikorsky RAH-66 Comanche was one of the first attempts at a stealth helicopter.
Limitations
Instability of design Early stealth aircraft were designed with a focus on minimal RCS rather than aerodynamic performance. Highly stealthy aircraft like the F-117 Nighthawk are aerodynamically unstable in all three axes and require constant flight corrections from a fly-by-wire (FBW) flight system to maintain controlled flight. As for the B-2 Spirit, which was based on the development of the flying wing aircraft by Jack Northrop in 1940, this design allowed for a stable aircraft with sufficient yaw control, even without vertical surfaces such as rudders.
Aerodynamic limitations Earlier stealth aircraft (such as the F-117 and B-2) lack afterburners, because the hot exhaust would increase their infrared footprint, and flying faster than the speed of sound would produce a sonic boom, as well as surface heating of the aircraft skin, which also increases the infrared footprint. As a result, their performance in air combat maneuvering required in a dogfight would never match that of a dedicated fighter aircraft. This was unimportant in the case of these two aircraft since both were designed to be bombers. More recent design techniques allow for stealthy designs such as the F-22 without compromising aerodynamic performance. Newer stealth aircraft, like the F-22, F-35 and the Su-57, have performance characteristics that meet or exceed those of front-line jet fighters due to advances in other technologies such as flight control systems, engines, airframe construction and materials.
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