The Federation of American Scientists offers this unique perspective into classified government aircraft, "some of which actually exist, some of which certainly do not, and all of which are fascinating in a way." This site is divided into two main sections. The first provides insight into several aircraft that were initially shrouded in secrecy but have since been revealed to the public. Some examples include the SR-71, the B-2, and the Hyper-X. The second section is devoted to aircraft that may or may not be currently under development or in operation by the US government. The much popularized Aurora is in this section, as well as exotic propulsion aircraft.