The supersonic Bomarc missiles (IM-99A and IM-99B) were the world's first long-range anti-aircraft missiles, and the first missiles that Boeing mass produced. The program also represented the first time Boeing designed and built launch facilities. It used analog computers, some of which were built by Boeing and had been developed for GAPA experiments during World War II. The missiles were housed on a constant combat-ready basis in individual launch shelters in remote areas. The alert signal could fire the missiles around the country in 30 seconds. The Model A had a range of 200 miles, and the B, which followed, could fly 400 miles. Boeing built 700 Bomarc missiles between 1957 and 1964, as well as 420 launch systems. Bomarc was retired from active service during the early 1970s.