@WT: I agree with you about the flaws that he has. However I feel that instead of making him reflect on his life this might make him finally give up. We got a small glimpse of him thinking about giving up just before he found the plane (after he fell off a cliff).
He wants to live without roots and obligations, and fly around the world in a plane. It definitely sounds fun and fulfilling, but does he have the money for housing and food, while he's flying? What about maintenance and fuel for the plane? If he doesn't have this money saved up in advanced, how is he going to pay for all of this? If he just 'ups and leaves' the farm, there goes his paycheck.
Just because something is your dream doesn't, by default, make it feasible or realistic. However, it can be adapted and become a reality, with some planning, and Rachael probably thinks he hasn't carefully planned this.
With everyone else being happy with their life and role in LL he is the only one (besides possibly Rachael) who doesn't have anything that makes him happy. All he has left is the dream of flying away and now Rachael just told him that she's not going with him. There's a possibility that he'll give this dream up, and if he doesn't have that then what does he have?
If Miles wants to have a working plane that he can fly, then great! It can be a hobby and, heck, maybe Mora will pay him handsomely to use it for dusting the crops or carrying shipments. However, just because he can't achieve everything that his pipe dream entails doesn't mean he should just give up on everything in his life, currently.
Frankly, if Miles were to give up on everything in life just because he has an unrealistic pipe dream, then that says more about him than it does about the people around him.