Britain's first jet bomber, the Canberra, has finally retired, after 55 years of service. The two engine jet, first designed as a bomber, was quickly adapted to reconnaissance and electronic warfare missions. So successful was the Canberra at this, that even the United States bought some 400 of them for that role as the B-57. The American Canberra's served from 1955 to 1981. Towards the end, the B-57 served mainly as an electronic warfare aircraft. In all, 1,352 Canberras were built. One reason for their popularity as recon aircraft, was their ability to fly high (up to 70,000 feet.) The 24 ton aircraft had a crew of three, and could stay in the air up to six hours per sortie. The internal bomb bay could hold 2.7 tons. This provided plenty of capacity for cameras, or electronic warfare equipment. In 55 years of service, fifteen nations used Canberras. While one of the most versatile and long serving warplanes, it is also one of the least known. The last combat assignment for Canberras was flying recon missions over Iraq.