Technicians conduct preflight inspections in the cockpit of a fighter jet, Xigaze, Tibet autonomous region, May 19, 2012. An engineering unit of the People's Liberation Army (PLA) Air Force has modified aircraft to make them adapted to the plateau environment in Tibet. The unit also wrote special plateau operations manuals to improve the aircraft maintenance work. [Photo/Xinhua]

Technicians conduct maintenance work and make preflight inspections at an airport in Xigaze, Tibet autonomous region, May 19, 2012. [Photo/Xinhua]