To meet military requirements the first civil production aircraft had four additional auxiliary fuel tanks in the main cabin which reduced the passenger seats to 26. The following batch of aircraft, designated C-54A, were built with a stronger floor and a cargo door with a hoist and winch. The first C-54A was delivered in February 1943. The C-54B, introduced in March 1944, had integral fuel tanks in the outer wings, allowing two of the cabin tanks to be removed. This change allowed 49-seats (or 16 stretchers) to be fitted. The C-54C, a hybrid for Presidential use, had a C-54A fuselage with four cabin fuel tanks and C-54B wings with built in tanks to achieve maximum range.