Built by Boeing, the B-52 became operational in 1955 as the Strategic Air Command's main long-range heavy bomber after its first flight on 15 April 1952. Nearly 750 B-52s were built before production ended in October 1963, including 170 D models. The D models were modified to carry conventional bombs externally, and later series had provisions for Hound Dog air-to-surface missiles and Quail decoy missiles. The B-52 set many records during more than 50 years of service, including the world's first non-stop round-the-world flight by jet aircraft on 18 January 1957, when three B-52s completed the trip in 45 hours and 19 minutes with only three aerial refuelings. In June 1965, B-52s entered combat in support of operations in Southeast Asia, and by August 1973 they had flown 126,615 combat sorties with 17 lost to enemy action. B-52s were stationed at Robins AFB from 1961 to 1983 with the 19th Bomb Wing, now the 19th Refueling Wing flying KC 136R refueling tankers. The aircraft on display served in Southeast Asia in 1968 and again from 1972 to 1973, flying numerous combat sorties with the 99th Bomb Wing from Andersen AB, Guam, and made its last flight on 25 August 1983 when the 7th Bomb Wing delivered it from Carswell AFB, Texas, to Robins AFB.