available, it became apparent that a group was too small to operate the base while performing the air defense mission. In April 1961 the 507th Fighter Wing replaced the 507th Group and assumed its assets, while adding additional support units, which were assigned to the wing's 507th Air Base Group (later the 507th Combat Support Group). In February 1962, ADC increased the alert requirement for its units. In addition to the two aircraft the wing had been maintaining on five-minute alert, one third of the unit's aircraft were placed on fifteen-minute alert. On 22 October 1962, at the beginning of the Cuban Missile Crisis, when President Kennedy announced the presence of Soviet intermediate-range ballistic missiles in Cuba. Continental Air Defense Command (CONAD) directed the dispersal of interceptors within the United States. The wing sent one third of its aircraft to Phelps Collins Field, Michigan. All group aircraft, including those at home and those at Phelps Collins were armed and placed on fifteen-minute alert status. The increased alert posture was maintained through mid-November, when CONAD returned units to their normal alert status, except for those under the control of its 32d Region, which controlled air defense in the Southeastern United States. The 4239th Strategic Wing was replaced in February 1963 by the 449th Bombardment Wing. Attrition (and the fact that production lines closed in 1961) caused a gradual drop in the number of planes assigned to interceptor squadrons, from 24 to typically 18 by 1964. The force reduction continued, finally resulting in a reduction in the number of interceptor units. In September 1968 the 507th Wing was inactivated along with the 438th Fighter-Interceptor Squadron, while its 507th Combat Support Group was replaced by the 4609th Air Base Group. Air Force Reserve Tactical Fighter In 1972 the Air Force Reserve began to receive Republic F-105 Thunderchiefs, which were becoming surplus to Air Force needs in Southeast Asia. To operate these fighters, it formed three tactical fighter groups, the first of which was the 507th Tactical Fighter Group at Tinker Air Force Base, Oklahoma, which was activated in May. Tinker was selected because the 937th Military Airlift Group there was slated to lose its Douglas C-124 Globemaster IIs, which were being removed from the inventory. The transition to the Thunderchief was the most difficult the Reserve had faced. In addition to the huge change from four reciprocating engine transports to supersonic jet fighters,