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.FIREPOWER: THE WEAPONS THE PROFESSIONALS USE - AND HOW. SUPER FIGHTERS, #41 Orbis Publishing 1990"They're Redesigning the Airplane", Micheal E. Long and James A. Sugar, National Geographic, January 1981, Vol. 159, No.1 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). , 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. , 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.

Electromagnetic emissions The high level of computerization and large amount of electronic equipment found inside stealth aircraft are often claimed to make them vulnerable to passive detection. This is highly unlikely and certainly systems such as Tamara and Kolchuga, which are often described as counter-stealth radars, are not designed to detect stray electromagnetic fields of this type. Such systems are designed to detect intentional, higher power emissions such as radar and communication signals. Stealth aircraft are deliberately operated to avoid or reduce such emissions.

Radar Warning Receivers look for regular pings of energy from mechanically swept radars while fifth generation jet fighters use Low Probability of Intercept Radars with no regular repeat pattern.

Vulnerable modes of flight Stealth aircraft are still vulnerable to detection while and immediately after using their weaponry. Since stealth payload (reduced RCS bombs and cruise missiles) is not yet generally available, and ordnance mounting points create a significant radar return, stealth aircraft usually carry all armaments internally. When payload bay doors are opened, the plane's RCS can be increased, diminishing stealth characteristics and making it vulnerable to detection. While the aircraft will reacquire its stealth as soon as the bay doors are closed, a fast response defensive weapons system has a short opportunity to engage the aircraft.

This vulnerability is addressed by operating in a manner that reduces the risk and consequences of temporary acquisition. The B-2's low observability makes it difficult for defensive systems to detect, track, and engage.

Some weapons require that the weapon's guidance system acquire the target while the weapon is still attached to the aircraft. This forces relatively extended operations with the bay doors open.

Such aircraft as the F-22 Raptor and F-35 Lightning II Joint Strike Fighter can also carry additional weapons and fuel on hardpoints below their wings. When operating in this mode the planes will not be nearly as stealthy, as the hardpoints and the weapons mounted on those hardpoints will show up on radar systems. This option therefore represents a trade off between stealth or range and payload. External stores allow those aircraft to attack more targets further away, but will not allow for stealth during that mission as compared to a shorter range mission flying on just internal fuel and using only the more limited space of the internal weapon bays for armaments.

Reduced payload

Fully stealth aircraft carry all fuel and armament internally, which limits the payload. By way of comparison, the F-117 carries only two laser- or GPS-guided bombs, while a non-stealth attack aircraft can carry several times more. This requires the deployment of additional aircraft to engage targets that would normally require a single non-stealth attack aircraft. This apparent disadvantage, however, is offset by the reduction in fewer supporting aircraft that are required to provide air cover, air-defense suppression and electronic counter measures, making stealth aircraft "force multipliers".

Sensitive skin

Stealth aircraft often have skins made with radiation-absorbent materials (RAMs). Some of these contain carbon black particles, while some contain tiny iron spheres. There are many materials used in RAMs, however generally the specifics as to the composition of the materials are classified.

Cost of operations Stealth aircraft are usually expensive to develop and manufacture. For example, the B-2 Spirit is many times more expensive to manufacture and support than conventional bomber aircraft. The B-2 program cost the U.S. Air Force almost $45 billion.

Countermeasures

Reflected waves

Passive (multistatic) radar, bistatic radar and especially multistatic radar systems detect some stealth aircraft better than conventional monostatic radars, since first-generation stealth technology (such as the F-117) reflects energy away from the transmitter's line of sight, effectively increasing the RCS in other directions, which the passive radars monitor. Such a system typically uses either low frequency broadcast TV and FM radio signals (at which frequencies controlling the aircraft's signature is more difficult).

Researchers at the University of Illinois at Urbana–Champaign with support of DARPA, have shown that it is possible to build a synthetic aperture radar image of an aircraft target using passive multistatic radar, possibly detailed enough to enable automatic target recognition.

In December 2007, SAAB researchers revealed details for a system called Associative Aperture Synthesis Radar (AASR) that would employ a large array of inexpensive and redundant transmitters and receivers that could detect targets when they directly pass between the receivers/transmitters and create a shadow. The system was originally designed to detect stealthy cruise missiles and should be just as effective against low-flying stealth aircraft. That the array could contain a large amount of inexpensive equipment could potentially offer some "protection" against attacks by expensive anti-radiation missiles (ARMs).

Infrared (heat)