Clayton Kuhles in Prescott, Arizona, USA has discovered over 20 crashed aircraft sites in the Himalaya area, all American, I believe. He combined his mountaineering love of physical challenges with his intrigue about missing aircraft and succeeded many times in reaching Hump crashsites never before visited by Westerners. Often the local people, who knew the land, asked him, "Why didn't anyone ask before?" before leading him to remote sites they had known about for decades.
Although the US government visited maybe two of the sites and collected some remains, by and large they stay away from collecting remains from obvious, positively identified wrecks, likely for political reasons. India and China dispute a large area of Arunishal Pradesh, and that seems to be at the heart of the issue.
Take a look at Clayton's website, where you can view photos from his numerous wreck visits. Warning: there are human bones in some photos.
http://miarecoveries.org/