I'm not disagreeing with anything you say. I just pointed out that it's not obvious what are the necessary costs of durable systems and engineering. As for my e

I'm not disagreeing with anything you say. I just pointed out that it's not obvious what are the necessary costs of durable systems and engineering. As for my example, I think it meets the criterion for a good example. Blackbird was not 'experimental', it was designed as a workhorse and functioned and operated as such.