As for going supersonic, they were probably lucky to have got away with it.
About four decades ago I monitored a contract with Douglas to provide aircraft for a project which they fulfilled with B-47 airframes. As the B-47s became unsupportable due to age, we asked Douglas to propose replacement airframes. They proposed used DC-8s. When we asked them to assure us of the structural integrity of the nominated planes they removed the wings from one and subjected the spar and other structural elements to detailed metallurgical analysis. The result: They could not detect that the plane had ever been flown. We accepted the planes as adequate for our purposes.
