This code will make you invincible for all the campaign missions and
the training mode.  What you have to do is this:
1. Go into Jet training mode
2. Kill the first two targets
3. When the second two targets appear quit
4. You are now invincible
If you want to turn off invincibility, all you have to do is go back
into training mode and finish the whole thing
Strategy for Knive's
Edge

On the level Knives Edge there is a boss who is very hard to beat. For
your bombs he takes very little damage. It almost looks almost
impossible to beat him.but there is a way me and my brother found out
how to beat him. first you have to get in battloid mode(the human
looking guy). first go and face him in sniper mode but kinda far away. charge
up the sniper and shoot him. once he tries to fire at you fly and go
strait above him that is the only place he cant shoot you. after a
while he shoots a building and causes a smokescreen and he disappears.
then little walking machines that look like at-st walkers in star
wars. kill them and follow the red dot on the radar. you will find the
boss again.do this continuously until he dies. this is the only way to
beat him that i know of.(you may find this in a strategy guide but i
swear I didn't look at that)