OK I'm no expert but...
1. Looks backlit and slightly blurred/out of focus/soft.
2. Also blurred/out of focus/soft.
3. Blurry/soft and the aircraft is too low in the frame. It's also dark.
4. I like this one but it's soft again and looks a bit bright 'cloudy'.
Don't worry though, they are decent attempts for a newbie. Do you use Photoshop? Search the forum for editing advice, there are some good workflow tips. Taking good aircraft shots is huge learning curve and you can take it to whatever level you desire. Practice and experience are essential but if you really want to get there I am sure you will.
If those are in the queue now I would take them out but don't let it put you off - it will improve your knowledge for next time.