The previous six Autobot Micromasters released in Japan as part of Operation Combination merge to become Sixtrain. Sixtrain shares a lot of similarities with Sixliner, but since several of his components have been retooled and repainted, he's considered a separate character. Sixtrain was available in a boxed set in Japan in 1992.
The combined form of the Universe Micromaster Aerialbots is Superion, an amalgamation of six robots plus their pack-in accessories that serve as connectors, head, and extremities of the gestalt warrior. While in Japan, the original source of the design ( Sixwing , 1992) was available in a collected set, this combiner needed to be purchased one bot at a time in the 2007 Universe release.
