Development of the Titan I began in 1955 when the U.S. Air Force sought a backup to the Atlas intercontinental ballistic missile in case that program failed. They wanted a larger, two-stage missile that could travel farther and carry a larger payload. The Titan I became the United States' first multi-stage ICBM, and although it was only a transitional missile, it played an important role in improving future Titans and other missiles. Powered by liquid-fueled engines that could send the missile and its nuclear warhead about 6,000 miles, it used a radio-inertial guidance system in which its trajectory was determined by commands transmitted between the missile and the ground control room. Fifty-four Titan Is were readied for launch in 1962 as a deterrent during the Cuban Missile Crisis, but their operational life was soon cut short by later missiles using safer fuels and more advanced guidance systems. By 1965, all Titan Is had been phased out and were either scrapped or distributed to museums, schools, and other facilities.