Also on the fighter aircraft thing: I'm not sure simulation is why present designs take so long. It's more likely a mixture of bureaucracy, cost-plus contracti

Also on the fighter aircraft thing: I'm not sure simulation is why present designs take so long. It's more likely a mixture of bureaucracy, cost-plus contracting creating perverse incentives to stretch out development, and insisting on pushing the envelope as far as possible and maybe past a point of diminishing returns. The latter might indeed involve a lot of gratuitous simulation and hard number crunching, but it's to get to places you just couldn't get with classical approaches. Of course you can debate the diminishing returns angle and whether that extra 5-10% performance is worth the effort.