While other aircraft, such as Air Force One, provide transport and communication capabilities, the E-4 is equipped for command and control operations. The Air Force contracted E-Systems to equip the aircraft with advanced communication and command systems, and the modifications included shielding against EMP and the installation of robust communication equipment. As the Boeing E-4B fleet ages (they’ve been in operation since the 1970s), the US Air Force plans to transition to the Survivable Airborne Operations Center (SAOC).