This cheats have to type while you are playing or when u pause the game by pressing 'ESC':
'iwannabe' - God Mode
'endisnear' - 9 Lives
'armorychamer' - All Weapons
'launchmenow' - All Missiles
'iamstronger' - All Power-Ups
'steelbirds' - Enable All Helicopters (not currently available)
'blindwarrior' - Enable All Levels (not available)
'messwiththebest' - Mission Complete!
'dieliketherest' - Game Over
'givemecredit' - Show Credits
Note: After using cheat-codes your rank will be 'cheater' and you will not be able to post your scores online.