The Boeing E-6 Mercury is an airborne command post and communications relay based on the Boeing 707. The original E-6A manufactured by Boeing’s defense division entered service with the United States Navy in July 1989. This platform, now modified to the E-6B standard, conveys instructions from the National Command Authority to fleet ballistic missile submarines, a mission known as TACAMO (“Take Charge And Move Out”). The E-6B model deployed in October 1998 also has the ability to remotely control Minuteman ICBMs using the Airborne Launch Control System. The E-6B replaced Air Force EC-135Cs in the “Looking Glass” role, providing command and control of U.S. nuclear forces should ground-based control become inoperable. With production lasting until 1991, the E-6 was the final new derivative of the Boeing 707 to be built.