Permission is required.
Think of A for “Above” (It’s above all the other airspace)
It’s not visible on the sectional charts. It starts at 18,000 MSL and goes to 60,000 MSL (FL 600).
Altitudes at 18,000 feet MSL and above, in Class A airspace, are commonly referred to in hundreds of feet as “Fight Levels,” abbreviated FL. For example, flight level two zero zero, or FL 200 = 20,000 feet MSL, FL 600 = 60,000 feet MSL, etc.
We can’t fly here anyway so we don’t need to focus too much on this airspace.