the big bombs, at least the 15,000 lb. "Daisy Cutter" are rolled out the back of a C-130...
http://www.csd.uwo.ca/~pettypi/elevo...s/b052-10.html
Less than 6 months after the B-52F became involved in combat in Vietnam, the Air Force decided to convert most of its B-52Ds to conventional warfare capability for service in Southeast Asia. Foremost among the changes needed was to give the B-52D the ability to carry a significantly larger load of conventional bombs. This led to the Big Belly project which was begun in December of 1965. The project increased the internal bomb capacity from just 27 weapons to a maximum of 8 4500-lb Mk. 82 or 42 750-lb M117 conventional bombs. This was done by careful rearrangement of internal equipment, and did not change the outside of the aircraft. In addition, a further 24 bombs of either type could be carried on modified underwing bomb racks (originally designed for the carrying of Hound Dog cruise missiles and fitted with I-beam rack adapters and a pair of multiple ejection racks), bringing the maximum payload to 60,000 pounds of bombs, about 22,000 pounds more than the capacity of the B-52F.