超音速巡航是指飞机在不开启后燃器之情况下持续进行超音速飞行。第一架能够维持水平超音速巡航飞行的是英国航太的闪电式战斗机。

早期在定义上，只要能在平飞状态下维持超音速飞行，就算是具备超音速巡航能力。但由于必须开启后燃器才能维持超音速，燃料耗损极为巨大，可达一般状态的数十倍之多，非常不经济。一般战斗机在后燃器全开下，大多数不到十分钟就会耗尽所有燃料。

由于现代引擎技术的提升，使得不开后燃器进行超音速巡航已经成为可能，在美国空军于1987年提出的先进战术战斗机（ATF）计划中，即将此一能力列为必备要求之一，因此现代的超音速巡航定义必须能不开启后燃器，否则就只能算是具备超音速飞行能力。

Supercruise is sustained supersonic flight of a supersonic aircraft with a useful cargo, passenger, or weapons load performed efficiently, which typically precludes the use of highly inefficient afterburners (reheat). Many well known supersonic military aircraft are not capable of supercruise as they are only able to maintain supersonic flight in short bursts (typically with afterburners) while they cruise at subsonic speeds. Aircraft such as the SR-71 Blackbird are designed to cruise at supersonic speed with afterburners enabled.