An air-to-surface missile (ASM) or air-to-ground missile (AGM or ATGM) is a missile designed to be launched from military aircraft at targets on land or sea. There are also unpowered guided glide bombs not considered missiles. The two most common propulsion systems for air-to-surface missiles are rocket motors, usually with shorter range, and slower, longer-range jet engines. Some Soviet-designed air-to-surface missiles are powered by ramjets, giving them both long range and high speed.
Guidance for air-to-surface missiles is typically via laser guidance, infrared guidance, optical guidance or via satellite guidance signals. The type of guidance depends on the type of target. Ships, for example, may be detected via passive radar or active radar homing, less effective against multiple, small, fast-moving land targets.
There is some cross-over between air-to-surface missiles and surface-to-surface missiles. For example, there was an air-launched version of the Tomahawk missile, superseded by the AGM-86 ALCM. Other missiles used in both roles include the Penguin and AGM-84 Harpoon anti-ship missiles. Many air-to-surface missiles can be used against both ships and land targets, although some must be modified to perform a different role; for example, the AGM-84E Standoff Land Attack Missile is a land-attack version of the Harpoon.