Riesenflugzeug
A Riesenflugzeug (plural Riesenflugzeuge, German for "giant aircraft"), sometimes colloquially referred to in English as an R-plane, was any member of a class of large World War I German bombers, possessing at least three aircraft engines, although usually four or more engines. These large multi-engine aircraft could fly several hours with larger bomb loads than the smaller Grossflugzeug bombers such as the Gotha G.V. Some of the earliest Riesenflugzeuge were given G-type designations before being redesignated, but a major distinction was that the requirements for the R-type specified that the engines had to be serviceable in flight.