1. Find plane ignition key: easy, medium, hard 
2. Destroy missile battery: medium, hard 
3. Escape in plane: easy, medium, hard 
4. Destroy heavy gun emplacements: hard 

Addendum 
Tank alert! There is a tank, which we neglected to mention in our early version of the strategy. It¹s also noticeable in the cut-scenes when the game has just started. It¹s excellent help when trying to finish off the 00 Agent level. We found it was best to use after we got ahold of the ignition key in the bunker. We suggest then getting into the tank and taking out all of the auto guns first, while trying to kill off men second. It¹s practically required in the 00 Agent level, but not in the Agent or Secret Agent level. 

Immediately behind you is a large crate of grenades. Grab the box. A guard is in a nearby room. Kill him and pick up the crate of mines. Head out into the snow by sliding through the snow chute at the far left end of the hallway. One guard is watching the area. Kill him and grab his KF7 Soviet. To acquire the plane key, walk left and enter the shed. Grab another crate of grenades just outside the door. After entering, turn right and two guards guard the plane key. Kill them, walk behind the table and pick it up. 

This level is unusual because all of the enemies is far away from you and yet there isn't a Sniper Rifle to be found (as far as we know). Stick to the left side of the runway, which is the side you're already on once you walk out of the shed. A soldier is guarding something obscure, and a pair of barrels are near him. Aim at a barrel just for fun, he'll die in the explosion. Run past him, shooting the next few guards, who are practically lining up, until you reach a nook in the wall. Hide here for a few seconds and switch your ammo to land minds. Across from you, in the distance, is a soldier or three, but your focus here is the missile battery nearest you. Throw a few mines at the machine gun battery, and run back to the crevice. They'll take out the gun and a guard. 

Now run back to the nook in the wall. Across the field is a single guard. Zoom in and dust him. By this time, about three to four soldiers are just about to greet you. Kill the closest soldiers first, then back up and wait. More will arrive. Use the leaning technique if you want. They come in waves. Dust the first and second waves and grab their guns. You'll pick up a Klobb, and you should switch to it. 

If you simply stay in that nook, the guards will never stop coming. You're next target is the missile battery across the runway, nearest the plane, so to get there you'll eventually have to stop killing them. It's hard to stop, isn't it? Eliminate a wave of them and then run. The best way to run is to strafe and run at the same time. It works. Head to the battery where you'll dispose of two guards. Switch to your mines. Throw a mine or two onto the battery itself, not the structure on which it rests. From far in the distance another machine gun battery is nicking you, and it's annoying, so in the medium level, run to the plane and touch it. In the hard difficulty, you need to blow them up. Use your mines, but be fast and stay out of its reach. Even better, use the mines. By the time you reach the plane, the second battery should blow. Check to see mission B completed. That should be the mission, in a nutshell.