Move the container so it blocks the door. Use the lever that you unblocked this way.
Use brake near the cart and move to the other side of the courtyard, hiding behind it. Enter the hangar.
There's Da Vinci's Bridge on your right. Take it and approach the tool box. There are Bolt Cutters in one of the drawers.
Use the Bolt Cutters to destroy the Padlock in a gate to the left of the airplane. Go in there to find a bandage on the table. Use the computer to move the crate below and go back to the main room.
There are two guards here, you'll have to fight them. Take some Flares from the shelf near the trapdoor. Open it and go down.
Go straight ahead, using more trapdoors when you see them. Eventually you'll reach a big gate that's out of power. There's another padlock gate a bit further, so make use of your favorite Bolt Cutters once again.
You'll reach a power box on the wall. Take 3 Fuses from it. Turn left to find yourself in a huge room filled with WW2 mechanisms. Turn right and find another Power Box. This time it will contain 2 Fuses, grab both of them.
Move to the opposite side of the room (don't go down the ladder yet) and use the ladder to go up to the control room. There's a First Aid Kit on one of the shelf (behind some bottles filled with chemicals). Use the elevator and take 3 Fuses that you find up there.
There will be a guard waiting for you in the control room. Take care of him, and go back to the main hall. There are 2 guards here, get rid of them, preferably one by one. Go down the ladder. In a dark corridor to the right you'll find a Mercury Coin.
Approach the electrical mechanism on the other side of the room. Use the UV Light on the blueprint on the wall. You can now examine the power box and use these Fuses you've been collecting to turn on the power. Use the switch nearby when you place the fuses as on the screen below.
Make your way back to the electric door you saw earlier. You'll see a guard on your way - ignore him for now and turn left, where he came from. In a dark niche you'll find a Mercury Sphere.
Take care of both guards that block your way to the door. Reach it and use the lever there.
Climb up the ladders twice to reach the ground level. There are two more guards before you. They're quite easy to sneak on. Approach the gas container and use Bolt Cutters on a Padlock. Turn the Gauge.
Take the ladder up to get to the roof of the nearby building. Defeat the last guard in there and throw a Flare from the edge to ignite an explosion. Well, that would be it.