Zeppelin-Staaken R.VI
The Zeppelin-Staaken R.VI was a four-engined German biplane strategic bomber of World War I, and the only Riesenflugzeug (giant aircraft) design built in any quantity. The R.VI was the most numerous of the R-Bombers built by Germany, and also among the earliest closed-cockpit military aircraft (the first being the Russian Sikorsky Ilya Muromets).