Martin 193
The Martin 193 was a design for a giant cargo transport seaplane that was conceived in 1942 as part of the "Sky Freighter" concept for colossal flying boats that could carry large loads of troops and freight across the Atlantic Ocean in response to the sinking of Allied merchant ships by U-boats. It was basically a 40% enlargement of the Martin JRM Mars, weighing 250,000 pounds (110,000 kg) at takeoff and featuring a longer hull and wingspan, being powered by six radial piston engines.