The US Air Force has awarded a $13 billion contract to Sierra Nevada Corp to build an airplane, reports Reuters. The US Air Force has awarded a $13 billion contract to Sierra Nevada Corp to develop a successor to the E-4B, known as the “Doomsday” aircraft because of its ability to survive a nuclear war. The Survivable Airborne Operations Center (SAOC) project is designed to replace the outdated 1970s-era aircraft, which are nearing the end of their service life. To meet the operational requirements, the weapon system will consist of a commercial jet engine hardened and modified to meet militar…