US Air Force awards $13bn contract to Sierra Nevada Corp to produce next-gen "Doomsday" plane.

The US Air Force awarded a $13bn contract to Sierra Nevada Corp to produce the next generation of the U.S. Defense Department's "Doomsday" plane, in part to be built in Colorado. The E-4B "Nightwatch" and National Airborne Operations Center planes are designed to keep top U.S. military officials alive during a nuclear attack. The current fleet of four planes has been in service since 1980.