The LGM-30G Minuteman III is a three-stage, solid-fueled, intercontinental-range ballistic missile. The U.S. has a fast launch time, nearly 100 percent testing reliability, and backup airborne launch controllers to preserve retaliatory capabilities. It entered service in 1970 with a force of 550 missiles. The United States is expected to rely on it through the 2030s. The Air Force requested proposals for a follow-on missile, the Ground-based Strategic Deterrent (GBSD) in July 2016.”]
Source: https://missilethreat.csis.org/missile/minuteman-iii/