During WWII, beginning in April 1942 until November 1945, when pilots tried to fly from India to China to resupply the Chinese war effort, they had a considerable challenge to fly over the Himalayan Mountains. The Hump was the name given by the Allied pilots in WWII to the eastern end of the Himalayan Mountains.

Creating an airlift presented the United States Army Air Force based in China the challenge, since it did not have units trained or equipped for moving cargo, and no airfields existed in the China Burma India Theater for basing that large number of transports that would be needed.

The challenge was made even more dangerous and difficult due to a lack of reliable charts, an absence of radio navigation aids and a dearth of information about the constantly chasing weather and wind patterns.

Causalities and loses over this time period included 594 aircraft lost, missing or written off and 1,659 personnel killed or missing. The operation began in April 1942 when Japan blocked the Burma Road, and continued daily until August 1945, when the effort began to scale down.

The final summary of logged flight time in the airlift totaled 1.5 million hours- the largest and most extended strategic air bridge (volume of cargo airlifted) in aviation history until it was surpassed by the Berlin air lift.

More Info: en.m.wikipedia.org