"but other alternatives (for example, hiring a thousand engineers and building a thousand planes a year) would have found the same answer" Before MacCready cam

"but other alternatives (for example, hiring a thousand engineers and building a thousand planes a year) would have found the same answer" Before MacCready came along, there were a thousand (well, a large number) of engineers building a thousand planes a year. But because these attempts were disjoint, there were all making the same mistakes and were slow to learn from them. The point of the article (as I understood it) is that when you're working towards a goal, you usually don't fully understand why that goal may be difficult to achieve -- what the real problems are. This is why is import to get early feedback about whether or not you're on the right track, and to adjust your attempts accordingly.