Which factor most directly determines the size of Class D airspace?

• A. The instrument procedures for which the airspace is established
• B. The airport's annual traffic
• C. The number of runways
• D. The presence of nearby Class B airspace

Answer: (A)

The size of Class D airspace is determined by the instrument approach and departure procedures used at the airport. These procedures define where IFR aircraft will be during arrival, approach, and missed‑approach segments, so the airspace around the tower is drawn to protect those operations in controlled airspace. If the published procedures require protection farther out or higher, the Class D area expands accordingly; if they’re more compact, the area can be smaller.

Airport traffic level, the number of runways, or the presence of nearby Class B airspace don’t set the dimensions in the same direct way. Traffic volume doesn’t dictate the protected volume, runways don’t automatically change the airspace footprint, and nearby Class B affects coordination and separation but not the fundamental basis for Class D’s size.