How to get to Tibet? At present, Chengdu is the busiest air hub to getting into Lhasa, Tibet. The major commercial flight routings (Beijing/Lhasa, Chengdu/Lhasa, Xian/Lhasa and Kathmandu/Lhasa) are monopolized by Air China. If the travelers wish to reach Tibet by land, there are few available roads to Tibet from Qinghai, Sichuan, Yunnan and Nepal respectively. However, the conditions of most roads are not good and the rides are quite tough.
http://www.tibettravel.cn/Tibet_Travel_FAQ.htm#4
