Hi, in former versions of the game, this feature was enabled. However the game became too easy, because the player was able to accumulate huge amounts on easy levels and then finish harder levels with ease when fully upgraded. But I'll consider that to enable this feature so the player has more options when he's stuck at difficult level.
Yes, If you destroy the airship you beat Red Baron, the airship has 1000 HitPoints so it is very difficult to destroy. Better way to destroy him is to use "Malicious parachute"
Once you buy "Malicious parachute" the game is easy. Just go close to enemy plane and cover it with that parachute. Best to fire the parachute when enemy plane has low altitude and doesn't have enough time to recover from stall.
Under rating threshold (hideshow)
I think this game has a nice concept as to the shop and varieties of planes it has. This game isn't very challenging although i like the stall feature. overall i would give this a 4/5