Okay, another question

How long does a Class 1 remain a class 1, before it is dropped down to a Class 2 and then a Class 3. Does this transition from a Class 1 to a Class 3 eventually void an ATP holder's ability to act as PIC if they are no longer within their Class 1 window, but have fallen down to Class 3.

I guess my question is this, simply put. If a Class 1 is valid for only 6 months, what happens to an ATP rated pilot after that 6 months when it becomes a Class 2? Do they have to go get another evaluation to get it bumped back up to a Class 1?

If it's confusing, I can re-word it. . . it's 3am, so . . . sorry.