Impressive game mechanics and idea. Playability needs to be tuned, to be playable for more than a few minutes. It has a grind that I found a bit too high for a game jam entry. But grinds also increase the happiness of success.
In my first two trials, I couldn't even dock on any cargos, and in my later trials I could score a few drops, so it's playable (if you are somewhat skilled, and patient).
I guess, with a bit easier altitude control, playability may increase.