The airport for La Paz, Bolivia, sits at 13,313 feet elevation and is the highest elevation airport in common use and is the reason many jets are certified for airports up to an elevation of 14,000 feet above sea level. Recently, however, the Cessna Citation XLS received approval to operate at airports up to 15,000 feet elevation. The flight inspection division of China's Civil Aviation Administration operates seven Citations and recently it made its first landing at the airport of Qamdo Bangda in Tibet which sits at 14,219 feet above sea level. The Citation XLS' certification is to 15,000 feet as there are no other runways in the world higher than that of Qamdo Bangda.
Source: Flying, July 2009. "Airways: Industry News & Notes", p17.