Thanks for the ideas Indagare.
1. I had thought about teleportation but figured it would not be good for mass use (maybe for a single kingdom but not everybody). So far I'm leaning to a mix of both options I said (have most land masses quite large but still make air travel decently common).
2. As for having the planet act as the plane of air honestly I had never even thought about that and is something I need to think on. I had planned to have a surface just make it extremely inhospitable (granted the common person would have no knowledge that it even exists), though still trying to decide what makes it that way (high gravity pressure, demons, covered in lava, ect).
3. Never seen that series and the wiki doesn't tell me much (not sure if its worth spending the money to try to buy it for reference material). As for having flying races, I was planning to have races that can fly / glide be allot more common but I also was hoping to use most of the standard races as well with just some lore tweaks. One of the reasons for using them is I would like to be able to use the same world no mater what rule set / edition my group may want to use (pathfinder, 3.0, 3.5, 4.0, D&D next, ect) it's much easier to swap a pathfinder elf with a D&D next elf then making my own races that may not work with some rule sets or don't have rules in place to make them for other rule sets. And lastly on this topic I have no problem screwing around with standard lore but I try to keep to a minimum on how much I mess with rules on how thing are / works, makes it a lot less hassle to bring in new players to a group when I don't have to give them a big print out of info going over new world specific rules / changes.
Sorry for rambling on a bit there but thanks for the ideas. It really helps me to think about other options or even just other angles to my own ideas as well as to add, keep, modify, or just get rid of ideas. Well thanks again for the help and any future help people give.