* CAA - This is the most common spelling and stands for Civil Aviation Authority.
* C.A.A. - This is another common spelling, especially in formal documents, and also stands for Civil Aviation Authority.
* CAa - This spelling is less common and is usually used when referring to a specific organization or company that uses the initials CAA.
So, to know how to spell CAA correctly, it's important to consider the context and what it refers to.