Thanks for the comments so far!
As for sharpening, I have been selecting the sky, then doing an inverse so as to only sharpen the plane. I then use unsharp mask. Is there a way to get the pictures a little sharper right off the bat other than an increased aperture? These were shot with either 5.6 or 6.3, I believe. Let me know how much higher I should go
Regarding the sun, it was actually quite low--these were taken around 6:30/7PM, and the sun was setting (a bit to the right of the nose of the plane if traveling in the direction of the plane), so the sun wasn't really very high.
With respect to zoom, these were taken with an 18-55mm lens, and the larger planes (737 and up) are usually taken without full zoom. From this side, I don't know if it's possible to get a good view further away--these were shot maybe 20-50 feet to the side of the center guiding lights. When the light is on the other side of the planes, I can shoot with a 70-300 lens, but the planes are higher, and give less of a side-on view.
I do appreciate the help so far!
Why yes, in fact, I am a rocket scientist...