Start the game with the parameter -enableconsole, e. g.

"...\Medal of Honor Airborne\UnrealEngine3\Binaries\MOHA.exe" -enableconsole

(Rightclick desktop icon of the game and and choose properties in the contect menu.)

Now in the game press [~] to open the command line, here you might type in:

god            God mode ON/OFF
fly            Fly mode ON/OFF
ghost          No Clipping mode ON/OFF
upgradeweapon  Weapon upgrade for all weapons
showhud        Show / hide HUD