Janet Airlines

Janet, sometimes called Janet Airlines, is the unofficial name given to a highly classified fleet of passenger aircraft operated for the United States Department of the Air Force[1] as an employee shuttle to transport military and contractor employees. The airline mainly serves the Nevada National Security Site (most notably Area 51 and the Tonopah Test Range), from a private terminal at Las Vegas’s McCarran International Airport. [19]

All Janet 737-600 aircraft are ex-Air China and with the exception of N273RH and N365SR which were previously operated by the now defunct China Southwest Airlines before being acquired for US Air Force operations starting in 2008.

Source: en.wikipedia.org