Although the B-52A was the first production variant, these aircraft were used only in testing. The first operational version was the B-52B which had been developed in parallel with the prototypes since 1951. First flying in December 1954, the B-52B number 52-8711 entered operational service with 93rd Heavy Bombardment Wing at Castle Air Force Base, California, on 29 June 1955. The wing became operational on 12 March 1956. The training for B-52 crews consisted of five weeks of ground school and four weeks of flying, accumulating 35-50 hours in the air. The new B-52Bs replaced operational B-36s on a one-to-one basis.

Early operations were complicated by lack of spares and ground facilities while ramps and taxiways deteriorated under the weight of the aircraft. The fuel system was prone to leaks and icing, and bombing and fire control computers were unreliable. The two-story cockpit presented a unique climate control problem – the pilots' cockpit was heated by sunlight while the observer and the navigator on the bottom deck sat on the ice cold floor. Thus, comfortable temperature setting for the pilots caused the other crew members to freeze, while comfortable temperature for the bottom crew caused the pilots to overheat. The J57 engines were still new and unreliable. Alternator failure caused the first fatal B-52 crash in February 1956, which resulted in a brief grounding of the fleet. In July, fuel and hydraulic system problems again grounded the B-52s. To avoid maintenance problems, the Air Force set up Sky Speed teams of 50 maintenance contractors at each B-52 base. In addition to maintenance, the teams performed routine checkups which took one week per aircraft.

On 21 May 1956, a B-52B (52-0013) dropped its first live hydrogen bomb (a Mk.15) over the Bikini Atoll. On 24–25 November 1956, four B-52Bs of the 93rd BW and four B-52Cs of the 42nd BW flew nonstop around the perimeter of North America in Operation Quick Kick, covering 15,530 statute miles (13,500 nm, 25,000 km) in 31 hours 30 minutes. The SAC noted that the flight time could have been reduced by 5-6 hours if the four inflight refuellings were done by fast jet-powered tanker aircraft rather than propeller-driven KC-97 Stratotankers. In a demonstration of the B-52s global reach, on 16–18 January 1957, three B-52Bs made a nonstop flight around the world during Operation Power Flite, covering 24,325 statute miles (21,145 nm, 39,165 km) in 45 hours 19 minutes with several in-flight refuelings by KC-97s. The 93rd Bomb Wing received the Mackay Trophy for their accomplishment.

The B-52 set many records over the next few years. On 26 September 1958, a B-52D set a world speed record of 560.705 miles per hour (487 kn, 902 km/h) over a 10,000 kilometers (5,400 nm, 6,210 mi) closed circuit without a payload. The same day, another B-52D established a world speed record of 597.675 miles per hour (519 kn, 962 km/h) over a 5,000 kilometer (2,700 nmi, 3,105 mi) closed circuit without a payload. On 14 December 1960, a B-52G set a world record by flying unrefueled for 10,078.84 statute miles (8,762 nm, 16,227 km). The flight lasted 19 hours 44 minutes. On 10–11 January 1962, a B-52H set a world record by flying unrefuelled from Kadena Air Base, Okinawa, Japan, to Torrejon Air Base, Spain, covering 12,532.28 statute miles (10,895 nmi, 20,177 km).

During this time, at the Strategic Air Command's peak strength in 1963, 650 B-52s were in operation in 42 squadrons and 38 air bases.

Vietnam War

With the escalating situation in Southeast Asia, in June 1964 28 B-52Fs were fitted with external racks for 24× 750 pound (340 kg) bombs under project South Bay. An additional 46 aircraft received similar modifications under project Sun Bath. In March 1965, the United States commenced Operation Rolling Thunder, and the first combat mission of Operation Arc Light was flown by B-52Fs on 18 June 1965, when thirty bombers of the 9th and 441st Bombardment Squadrons struck a communist stronghold near Ben Cat in South Vietnam. The first wave of bombers arrived too early at a designated rendezvous point, and while maneuvering to maintain station, two B-52s collided, resulting in the loss of both bombers and their eight crewmen. The remaining bombers, minus one more which turned back due to mechanical problems, continued on towards the target, which was bombed successfully.

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