Great little game, some more polish and levels and it would be even better, reminds me a lot of an old ZX Spectrum game called Cyclone (yup, I'm that old!) check it out:
Viewing post in Jim's Jam Aerial Delivery Service jam comments
If I was to extend it, I would create more locations and use some sort of procgen to create missions (at least after the 'training' mission).
But not sure how I would extend the play beyond being a series of 'fetch quests'... which I added to make some game play... I started out with just a flight simulator... and then said to myself... maybe I should add some gameplay. .. <shrug>