1. Go up the ladder in the blue building. Drop out of front window onto a small ledge along the front of the building. You can jump onto the open window too. It isn't a great spot.

2. Besides the planes mentioned in my previous submission, you can get up the other 2 sections as well. One is fairly hard to get up and you are too exposed. But the one with the wing-stub sticking straight up is decent to get upon. From the building-side of this section walk up to the right corner of the outside of this section. Just jump while pushing forward and your guy will make it up top with ease. Hide behind the wing-stub and shoot down through the holes (windows?).

3. If you climbed on top of the giant u-shaped plane areas (from my previous submission), run towards the tall blue building (mentioned above) and jump onto the junk piled up in front of that building. Most people will not see you camped up there.