I remember reading in a Skunk Works book that they had a custom toolset for working on the SR-71. I imagine needing custom tools ends up being pretty common for cutting-edge military aircraft.
Here's my question: at what point do aircraft designers realize that they're going to have to mold and cast custom toolsets to fabricate an airplane? Does it happen at the design stage, while the aircraft is still on paper? Or do they start with off-the-shelf parts and ultimately the tools go through several iterations?
I'm asking because I am curious if a similar approach to the requirements/design lifecycle of can be taken for development of custom tools in support of a larger software project.