There are a lot of things that can improve reception (no case, where it may be mounted in the plane, the way you hold it 😉, etc. etc.).
But I'm guessing that your issue is more a proximity to towers? I may be incorrect here, but a lot of non commercial pilots tend to fly in areas that are a bit more remote than the metro areas that have dense tower locations.
You could try turning off the 3G option, and see if you get better data on Edge (but it will be very slow).
HTH.