A set of techniques used by some military aircraft to avoid being detected by enemy air defences.

Stealth refers to the technologies used for making military aircraft harder to detect, mainly by making them less visible to ; as radar is the primary means of detecting attacking aircraft, making a fighter or bomber harder to pick up on radar gives it a better chance of surviving a mission or missions without getting shot down.

There are several different ways of making aircraft stealthier:

  • Most stealth aircraft are carefully shaped so that, if radio waves emitted by an enemy radar strike the aircraft, very little of the signal is reflected back towards the radar installation; most of the radio waves bounce off in other directions. To achieve this, some early stealth aircraft (such as the F-117 "Nighthawk") had a very angular, faceted appearance; advances in the software used to find stealthy shapes have enabled newer stealth aircraft to have smoother, more aerodynamic shapes.
  • Stealth aircraft have to take great care to avoid maneuvers that would present large flat surfaces to an enemy radar, as this would greatly increase the aircraft's visibility to said radar.
  • Some aircraft are painted with materials that absorb radio waves rather than reflecting them; the compositions of these materials are generally tightly classified, but are thought to often contain microscopic spheres of substances such as iron or carbon black.
  • Stealth aircraft generally lack large protrusions, as these tend to be good radar reflectors; instead of carrying bombs and missiles on external hardpoints, stealth fighters and bombers carry all of their munitions in an internal bomb bay.
  • To prevent passive radar receivers from picking up the aircraft's own radio transmissions (and thereby possibly allowing enemy forces to determine its position and movement), stealth aircraft use special radars that send out pulses of radio waves at irregular intervals at random frequencies and intensities, rather than regular strong pulses on a single frequency, and generally maintain strict radio silence in combat zones except in dire emergency.
  • Other aspects of stealth include reducing or disguising infrared emissions from an aircraft's engines (thus making it harder to target with ), painting it dark colours and operating at night to make it less visible to the naked eye, and using quieter engines and avoiding flight so as to make it harder to hear it coming.