The E-6B Mercury is a military aircraft used by the United States Navy for command and control missions. It is based on the Boeing 707 airframe and is equipped to communicate with submarines and strategic forces. The aircraft plays a crucial role in the Navy's nuclear deterrent strategy. Equipped with advanced communication systems, the E-6B can relay orders from the President and Secretary of Defense to submarines while they are submerged. This capability ensures that U.S. strategic forces remain connected and responsive during crises, enhancing national security and military readiness.