Most C-87s were operated by the U.S. Air Transport Command and flown by formerly civilian crews from U.S. civil transport carriers. The planes were initially used on transoceanic routes too long to be flown by the C-47. After the Japanese invasion of Burma in 1942, the C-87 was used for flying war material from India to American and Chinese forces over The Hump, the treacherous air route that crossed the Himalayas. When the route was established, the C-87 was the only readily available American transport with high-altitude performance good enough to fly this route while carrying a large cargo load.