That's a good point. I think we know enough about building things that fly now and we can do it quickly and cheaply enough that we can build prototypes that fail, and iterate until we get it right.

I could be wrong, but I think that was less of the case in the past. Or perhaps we just didn't know better. Building big expensive things that can kill lots of people - I'm thinking infrastructure, commercial planes, etc - comes along with the idea that we should know ahead of time how we will make it safe without it failing. We can't build a prototype of a skyscraper in a city and have it fall on people. But perhaps the way we engineer those types of things could borrow a lot more from agile than I was initially claiming.