Your on a great track so far! After seeing some more wires, it's time to add my two cents.
When creating models that will be used in a game engine that uses vertex lighting, it is important to have even edge flow over every model so that it lights evenly across the mesh. On the same token though, edge edge must be used with a purpose. If you can do without it, get rid of it unless you really need it to keep a balanced lighting solution (example: A long hallway would need more poly's than just one long one for the walls). Having said this, I think you can still squeeze a few poly's out of your models.
On the helicopter in particular I'm noting a long of triangulation that shouldn't be happening along with a few edges you can do away with. The middle edge loop cutting through your model can be removed, unless you have or want that raised and it's adding value to the model. It's hard to tell without being able to rotate it around. Also, the highlighted areas are a big wtf.
This is what your edge flow should be looking like after the changes. The green tri lines can be turned either way, I just did it so you can get an idea.
Let's work on this one and then move onto the others. If you need any help cleaning up the geometry, just let me know. I bet we can drop the poly count on that command center to 500 or so. A lot of poly's can be removed from your other models as well.
EDIT: I'd also like to mention something else as well. For poly's that will NEVER be seen, delete them. Why add it to the polygon count if it's not important? Why have one more item on your UV template if you can delete it to save room for others? Sometimes doing this is taking things too far, but it's a good tip none the less.
"If I have seen a little further it is by standing on the shoulders of Giants" - Isaac Newton
-Computer Animation Major @Baker.edu-
