If resources in deploying weren't an issue, here's what I'd do to enhance the odds of keeping a new player.
[edited out one part]
Have a set of offline missions: intercept and shoot down incoming enemy fighters, intercept and shoot down incoming enemy bombers, capture an undefended base, shut down an airfield's ord, shut down an airfield's vh and fighter hangars.
Have a beginner's arena, with planes having ammo only as long as the player's number of kills is below some threshold.
Have default settings be with stall limiter enabled (although this might be the default already).
The edited out part is below, which I wouldn't do until well after doing the above (to see if it is even useful to do it -- it very likely could be a lot of work for absolutely no benefit, with the beginner's arena being much more important):
Have an offline training system available. It would be a series of courses, each one fairly brief, that a player could go through and then get a pass or fail on it (like in the game mentioned by Slate in his post) with the software keeping track of whether or not the player passed or failed (so that he can work on it over time). It would cover topics from basic to more advanced, such as, for fighters: take off and takeoff in loaded fighter/bomber, landing, CV takeoff and landing and CV takeoff in loaded fighter/bomber, navigating to an area where a fight is going on (i.e., practice with sector counters, radar, flashing bases, and sector numbering), entering and recovering from stalls, entering and recovering from spins, basic maneuvers (roll, loop, immelman, split s, high yo yo, low yo yo, turns maintaining edge of stall, turns maintaining near blackout), shooting several unmaneuvering AI target planes, shooting AI planes with very poor combat skill, shooting AI planes with mediocre combat skill, shooting down some AI bombers with no escort and with mediocre gunnery skill, divebombing some targets and strafing some ack, and so on. Similar course for bombers and for GV's.
