Congratulations on your success! Whenever the thought: "Perhaps I'm waking up now" crosses your mind, you will wake up. Don't even think about your body in bed, if you might be stuck in a coma (you don't dream in a coma anyways) or things like that. Just go with the flow, and keep yourself anchored to the dream by doing some stabilization techniques now and then.

I also have trouble staying in the dream when I fly. Short flights work for me though, and perhaps if you keep your eyes on the ground while you do it, you'll have an easier time staying in the dream.

Don't get discouraged if you don't manage to stay in the dream for more than a few minutes in the beginning, a few minutes of lucidity is gold. I still don't have more than 20 minutes long ones, and I've had more than 100 LD's since I started.

Got any more questions? Don't hesitate to ask. Good luck and keep on dreaming!