Project E nuclear warheads were also used on the sixty Thor Intermediate Range Ballistic Missiles (IRBMs) that were operated by the RAF from 1959 to 1963 under Project Emily. During the Cuban Missile Crisis, the RAF's bombers and Thor missiles targeted 16 cities, 44 airfields, 10 air defence control centres and 20 IRBM sites. The RAF high command never warmed to missiles, and always ranked them secondary to the V bomber force. The missile bases were separate from the rest of the RAF and its personnel considered outside the mainstream. Project Emily gave the RAF considerable experience in missile operations, but the 1960 cancellation Blue Streak in favour of the American Skybolt, an air-launched ballistic missile, rendered this expertise of dubious value. An Air Council meeting on 31 May 1962 decided that Project Emily should be terminated by the end of 1963, and the last Thor squadrons were inactivated on 23 August 1963.