The AGM-158 JASSM-ER is an air-launched cruise missile that became operational in 2014. Unlike its predecessor, which used a turbojet engine, the JASSM-ER utilizes a turbofan engine similar to those found in tactical fighter planes, and has an internal structure that allows for additional fuel storage, increasing its range from around 230 miles to over 620 miles. The missile is guided by an internal inertial navigation and GPS unit for most of its flight, which was originally developed for weapons such as the AGM-154 Joint Standoff Weapon. Once the missile reaches its target, it switches to an infrared seeker for terminal guidance.