The Boeing Company continues to support the E-4B National Airborne Operations Center for the U.S. Air Force and U.S. Strategic Command, modifying the third of four E-4B aircraft at its Wichita, KA, Support Systems facility. The aircraft is receiving Programmed Depot Maintenance and a Mod Block One upgrade, which adds a state-of-the-art communications infrastructure that enables leaders to communicate securely with other air- and ground-based executive command and control facilities. The E-4B, a modified Boeing 747-200, is a modern, highly survivable command, control and communications center used to direct U.S. forces, execute emergency war orders and coordinate civil authority activities.