The only known missile of this type that was intended for operational service, the GAM-87 Skybolt, intended to be launched from B-52 Stratofortress and Avro Vulcan bombers, was in development by the United States Air Force, with the United Kingdom as a customer. In 1962, with technical difficulties and costs mounting, the program was cancelled, with the United States and the UK concentrating on the UGM-27 Polaris submarine-launched ballistic missile instead.