I loved it, too. Although it got quite boring after a while (but this happens always).
I actually finshed being 3rd with a rather risky tactic. I initially decided to NOT order new aircrafts, but use old 737-300 instead. Many of these were around 27-28 old when the game ended - and I had more than 100 of those. This tells me that aircraft age has no big overall affect, although maintenance can get expensive. Since I had 400+ other brandnew aircrafts, this didn't bother me a lot, though. Money came in just nicely. If the game world would have been a bit longer, I would have had a big problem with all those ancient 737...
I also decided to order new Q400 instead of Q400 NextGen which initially helped getting aircrafts fast and much cheaper because everyone else went for the NextGen (which is almost the same anyways).
I'll probably stick to the US market as I like having a national airline. This game world had so much demand that I didnt know how to fulfill it.