Were I the folks in charge at Boeing, I'd be looking at a joint venture with Mr. Musk, starting today. I suspect that the difference in estimates are owed to the usual testing phenomenon---you test for what you can imagine and that is heavily conditioned by your expectations. Same reason that the folks who write software/engineering/whatever should never test it. You need a team who's main goal in life is to ruin someone else's day. When I worked for EA, the testing team was the biggest PIA you could imagine. But if they could come up with bugs, imagine what real life could do. (Pesky 8-year old kids...<grumble/>)