Definition
Extensions of Class D surface area airspace that protect aircraft on published instrument approach procedures into the primary airport. When the extension is two miles or less, it is considered part of the Class D airspace. When the extension is more than two miles, the extension itself is Class E airspace.
Plain English
Extra strips of controlled airspace tacked onto the end of a Class D area to keep arriving instrument traffic protected while they line up for the runway. Short ones (two miles or less) stay Class D. Longer ones become Class E.
Context Anchor
Seen when studying Class D airspace shapes around towered airports, especially airports with published instrument approach procedures.
Why Pilots Care
Keeps arriving aircraft inside controlled airspace so ATC can provide separation and traffic advisories farther from the airport.
Grounding Statement
Picture the main Class D airspace as the area around the airport, with narrow added pieces reaching outward along common arrival paths.
Intuition Check
Do not read “arrival extensions” as extra time for arriving traffic. Here, it means extra airspace added to the main airport airspace area.
Example Sentence 1
The instructor pointed out the arrival extensions on the sectional and explained why the longer one was charted as Class E.
Example Sentence 2
The sectional showed two arrival extensions aligned with the main runways at the towered field.