Stealth aircraft 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 an obvious 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
Swept wing air in front of the aircraft begins to compress. This creates a force known as wave drag. This wave drag increases steeply until the whole aircraft is supersonic and then reduces. However, shock waves can form on some parts of an aircraft at a speed where the aircraft is moving at less than M=1.0 because the "local" speed of sound is determined by air temperature. A rapid drop in air density caused by aircraft contours will reduce the local air temperature and will correspondingly cause a drop in the local speed of sound that can cause shock waves to form.