Mars Needs Babies!
The Martian race is dying out and is in desperate need of young DNA to continue to procreate. Human DNA is sufficiently similar as to be usable, so the Martians have begun coming to Earth to harvest infants.
Humans have taken to hiding their young in difficult-to-reach places, taking advantage of the fact that the Martians can’t exit their limited mobility landing craft.
As the newly-minted pilot of one such craft, your job is to (initially) complete the training levels: getting your craft from point A to point B.
Once you have completed your training, you’ll be dispatched to Earth to attempt to evade the Humans’ deadly defenses and navigate the labyrinthine structures they are using to protect their young. You’ll need to get from A to B, pick up your precious cargo, and return to A to deliver the (baby) bootie.
Possibly earn some sort of credits for upgrades to your ship (more fuel, easier rotation, etc).
Possibly some mechanism for picking things up at B and returning them to A.