Formation Z was initially an Arcade game, created by Jaleco in 1984. It was eventually ported to MSX and Famicom, with the Famicom version reappearing in the PS1 compilation Jaleco Collection Vol 1 and on the Wii Shop's Virtual Console. It is thought to be the earliest game in which the player could transform between a robot mode and a vehicle mode: Future games that would use this concept include Square's Thexder and, of course, Takara's various Transformers games.
In the game, the player can run across the ground in their robot mode, or take to the skies as a jet with limited fuel. The game scrolls a lot faster as the jet, though the player is also more maneuverable to compensate. In some cases, one of the two modes are inaccessible, so the player is required to switch occasionally. Formation Z is notable for being one of the first horizontal-scrolling shoot-em-ups to have some degree of vertical scrolling as well, as the jet could take to the skies far above the ground.
Formation Z was the second game Jaleco ever published for the NES, following their earlier Arcade conversion of Exerion. In both cases, Jaleco used third-party developers to create the NES versions.