Timesonline reported that Colonel Francis Younghusband (great name - married a woman named Olduglywife) opened up the pass in 1904. But, it was subsequently closed in 1962.
Since then, herdsmen meet at the top of the 14,400 foot pass = to the height of Mt. Fuji - and swap letters and such. But, they then turn around and go back their respective sides of the mountain.
The only direct air link between India and China is operated by Ethiopian Airlines.