Enable Cheats:
When are still on the platform (the boat) and you just entered the mission, press ESC, then type Waterfall, press ESC once again to enable the cheats. Now you have unlimited weapons and armour so you won't crash until you put the cheats off (press F12 to do that)

Other small cheats:
first of al do what stands above (ESC, waterfall, ESC) after that press the following to get something special:
Q - Skip to another mission.
T - Doubles the speed of your helicopter

Here are the passwords that you can enter in the main menu of the game to start in level x:
CMMKBMMMJ - Go to level 2
CMN-BMMMZ - Go to level 3
CMBRNMMM5 - Go to level 4
CMVBBMMMG - Go to level 5