Max Clearance is an upgrade available only to Allied Construction Yards and Command posts.
Once researched, it opens the 3rd and final tier of the Allied Arsenal. However, a Defense Bureau is required to unlock some units.
Note that the upgrade has only a local effect, meaning that if the Construction Yard has researched Max Clearance then it will only affect production buildings in its vicinity only.
However, you can research the clearance via command posts themselves if you want to grant your production buildings with improved clearance at the cost of researching the same upgrade individually.
|Boot Camp||Armor Facility||Airbase||Seaport|
|Tanya*||Athena Cannon||Century Bomber||Aircraft Carrier|
|*= Requires Defense Bureau|