The majority of people playing our game either haven't played a flight sim in years or haven't ever played one. I'm all for ideas for how to introduce the concepts of flight to someone but repeatedly killing them in the first missions just quickly gets annoying. We'd probably lose far more players to "It's too hard, I didn't pay for this so there's no reason to go back to it"
Probably a simple yet comprehensive training campaign that explains the mechanics and massages newcomers? (The main problem I'm seeing with this is like every other flight sim I've played save for Microsoft Flight Simulator, they're fully optional and don't drive the plot as much as I would hope.)
I remember MicroProse's hella old F-15 Strike Eagle II manual, they did a fine job of condensing how a lot of things work (but I don't see a manual or ref sheet for this mod coming out anytime soon).
This is what I gathered up for thought after looking from training missions from F-22, Jane's USAF, and MechWarrior 3 (if you guys have any better idea on how to streamline/condense/replace this, be my guest):
Day 1: Touch and Go - get to know your fighter (introduce to the basic flight controls, basic maneuvers, such and such).
Day 2: Basic Target Practice - mock Air to Air training, explaining how your weapons systems work (if there's no feasible fighter only bombing operations so you can do Air to Ground, probably put that under Combined Arms training).
Day 3: Advanced target practice / flying techniques (probably feature the glide maneuver, evasive tactics and other flight tactics, such as the Scissors Turn and jinking).
Day 4: Tactical Training - Coordination and communication with friendly assets/wingmen (make your fighter unarmed and let your squad do the work, unless you want to make sure that the player is a leader who can fight as well as communicate), and possibly Combined Arms training (working in tandem with a capital ship asset if you're not going to do bomber ops).
Day 5: Graduation Day - featuring live ammo, try to imagine a complete theater of a real-world-ish combat scenario, something like the Red Flag program.
Very few people like reading the manual to discover everything a product can do before they turn it on...
Wrong.
The sooner you ditch the tutorial-system in favor of the above or something else the better off you will be.
I do not think "not having any players anymore" is the best off Diaspora can be.
Oh god, this is making me recall
Knights in the Nightmare. (That was literally one of the handheld games in which if you didn't either read the manual or do the optional in-game tutorials to get how the game worked, you'd be boned.)