Hold Left Shift and press Keypad - at the indicated screen. Release
the keys, then type one of the following codes to activate the corresponding cheat
savegame - Saves Game (Gameplay Screen)
endmission - End Mission (Gameplay Screen)
campaign - Unlock Levels (Main Menu)
topography - Unknown Effect (Gameplay Screen)
Start your mission and go until you get to the helicopter. Wait a few seconds
and jump out of the helicopter. Jump out before they start screaming about the
helicopter getting hit. You will become invincible until you go to the Target
area and finish the level.
Thanks to Revolution readers Jobe and Hugo!