[Llarry]

The USA, aware of the Canberra's excellent altitude capabilities, thought "what if we gave the B-57 (American variant of the Canberra) more wing" and came up with the RB-57D. Weight is the enemy of altitude and unfortunately the wing was not up to the task. Several aircraft suffered broken wing spars, which led to the retirement of the RB-57D and the development of the RB-57F.

Here's a dramatic photo of an RB-57D sampling radiation from a nuclear test; the mushroom cloud is visible in the background.