On a Friday in 1948, six aeronautical designers from the Boeing Company holed up in a hotel suite in Dayton, Ohio. They stayed put until Monday morning, except for the one who left to visit a hobby shop and returned with balsa wood, glue, carving tools and silver paint.

The group emerged with a neatly bound 33-page proposal and an impressive 14-inch scale model of an airplane on a stand. Col. Pete Warden, the Air Force chief of bomber development, studied the result and pronounced, “This is the B-52.”

One of those six was Holden Withington, and on Dec. 9, at age 94, he became the last of the B-52 designers to die. His daughter, Victoria Withington, said he died at his home on Mercer Island, Wash. He had Alzheimer’s disease.

It takes a vast team of experts to design a complex airplane, particularly one like the B-52 Stratofortress, with its eight engines and radically swept-back wings. Mr. Withington, called Bob, played down the achievement, saying it evolved from earlier plane designs and not a little luck....