Alright, let me give you some of my tips for each picture.
Allegiant 757-200: The photo has great lighting! The only thing you need to fix is the crop and some contrast.
Republic E175: It seems a bit over exposed. Try using AV mode with ISO 100 and F9. Crop would also help. Great composition, however.
Fedex DC10: Great composition! Love that smoke! However, it seems a bit backlit. If there is another spot where you could get that angle on the other side, that would be your best bet.
Delta 757-200: Nothing I can say is wrong with that one! Maybe a tiny bit over exposed, and the aileron was cut off but thats minor.
Delta MD88: PERFECT SHOT!
Delta MD88 (second shot): It looks a little under contrasted and grainy. Easy fix in LightRoom.
Frontier A319: Overexposed and bad crop, Easy fix though ;)
DL 175: Just minor crop adjustments needed. Good picture.
Fedex A300: Backlit. Try and aviod those pictures.
American A319: Just fix the crop a little, great picture!
If you need any advice, be sure to check my photography guide.
Great pictures! Can’t wait to see more!