I've had this game for 10 years and I still play on it!
The game has 4 training and 12 'proper' levels which cover everything from air to air combat to strafing annoyingly small tanks and dropping laser guided bombs. The missions vary in difficulty, some easy, others like the last level, are annoyingly hard.
The damage your A-10 'Tankbuster' can take is realistic (as far I as I know). You can activate a checklist thing which tells you what is Okay and what has been damaged (if you can't see it already). The visible damage is good and your plane can lose engines, wing tips, tails and landing gear. The only thing I haven't got to the Malfunction setting yet the the gun (i think it's impossible). If you ever get this game, I highly recommend you read the instructions (which install with the game) as some of the controls are quite advanced. It took me over a year to work out that F1 to 11 arm the weapons. The game is a masterpiece in my opinion but there are probably modern flight sims which I haven't played on which are just as good.
To conclude, If you get a chance to play this game, take it. It won't cost more than a few pennies.