In 1941 the U.S. Army Air Forces selected a modified version of the DC-3, the C-47 Skytrain, to become its standard transport aircraft. The U.S. Navy version was the R4D. R4D modifications included a reinforced fuselage floor, the addition of a large cargo door, the fitting of cargo hooks beneath the center wing section and the removal of the tail cone to mount a hook for towing gliders. As a supply plane, the R4D could carry up to 6,000 pounds of cargo. It could also hold a fully assembled jeep or a 37 mm cannon. As a troop transport, the R4D carried 28 soldiers in full combat gear. As a medical airlift plane, it could accommodate 14 stretcher patients and three nurses.