"The Hump" was a high altitude military aerial supply route over the Assam Valley in northeastern India, across northern Burma, to Yunnan province in southwestern China. This operation was the first sustained, long range, 24 hour around the clock, all weather, military aerial supply line in history. It was a start-from-scratch operation. There was no precedent for it.

The Hump route was an unlikely route for regular flight operations due to high terrain and extremely severe weather. It crossed a north-south extension of the main Himalayan Mountains that ran south through northern Burma and western China. On the very north end of the extension terrain exceeded 20,000 Mean Sea Level in height. Average elevations lowered to the south but did not fall below 12,000 Mean Sea Level for approximately 140 miles. The routes flown fell between these two extremes.Northern Burma was largely uninhabited except for wild native tribes. In addition to mountains, it was covered by tropical rain forest with trees reaching over 150 feet in height. River gorges of the Salween, Mekong and Yangtze Rivers exceeded 10,000 feet in depth. Uncivilized headhunter tribes existed on the southern rim of the main Himalayas in China.Severe weather existed on the Hump almost year-round. The monsoon season, with heavy cloudiness, fierce rain and embedded severe thunderstorms with turbulence severe enough to damage aircraft, existed from around May into October of each year. The late fall and winter flying weather was better with many VFR days. However, heavy ground fogs, with ground visibilities down to zero/zero, occurred almost nightly during the early winter, and severe thunderstorms still occurred over the route on an irregular basis. Winter winds aloft were extreme, often exceeding 100 mph. Most night flying had to be done by instruments from takeoff due to lack of any ground or horizon references, until well into western China.Source: China-Burma-India Hump Pilots Association