AIM 3-1-3

When overlapping airspace designations apply to the same airspace, the operating rules associated with the more restrictive airspace designation apply.

For the purpose of clarification: Class A airspace is more restrictive than Class B, Class C, Class D, Class E, or Class G airspace;

Class B airspace is more restrictive than Class C, Class D, Class E, or Class G airspace;

Class C airspace is more restrictive than Class D, Class E, or Class G airspace;

Class D airspace is more restrictive than Class E or Class G airspace; and

Class E is more restrictive than Class G airspace.