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>
multiplayer definitely could be done..
but from a practical side of things, I do gam jams as a hobby... so I am not sure how much more time I want to put into this. Feel free to follow my account or the game, so if I do work more on it, you can get notified.