Definition
The ranked order of U.S. airspace classes used to determine which class applies when two or more overlap. From highest to lowest, the order is Class A, Class B, Class C, Class D, and Class E. When airspace of different classes overlaps, the rules of the more restrictive (higher-ranked) class apply within the area of overlap.
Plain English
When different types of controlled airspace cover the same piece of sky, this is the pecking order that decides which set of rules wins. The stricter type always takes priority.
Context Anchor
Seen when studying controlled airspace, sectional charts, and areas where airspace boundaries overlap around airports or busy traffic areas.
Derivation
Hierarchy comes from Greek hierarkhia, meaning a ranked order. Here it simply means airspace classes are ranked, and the higher-ranked class governs the shared area.
Why Pilots Care
Knowing the hierarchy prevents inadvertent entry into controlled airspace without required clearances or equipment and supports safe, legal flight planning.
Analogy
Think of it like road signs at the same location. If one sign says the normal speed is 55 but another says a work zone limit is 35, the stricter rule controls.
Intuition Check
Do not assume airspace hierarchy means airspace arranged by altitude or importance. Here it means the order used to decide which operating rules apply when airspace classes overlap.
Example Sentence 1
Because of the airspace hierarchy, when Class D and Class E overlap, Class D rules apply inside the shared area.
Example Sentence 2
Understanding the airspace hierarchy helped the student pilot select a practice area in Class G airspace that required no radio contact.