Definition
Airports that handle a very large volume of arriving and departing IFR traffic, requiring structured route, altitude, and flow management to keep operations safe and orderly. The FAA designates certain busy airports — such as those serving major metropolitan areas — as high density terminals, and publishes Preferred IFR Routes into and out of them to organize traffic and reduce controller workload.
Plain English
These are the busiest airports in the system. Because so many aircraft are coming and going, the FAA sets up specific recommended routes to keep traffic flowing smoothly.
Context Anchor
Seen in discussions of Preferred IFR Routes, where the FAA explains why certain routes are published between busy airport areas.
Derivation
‘Density’ comes from Latin densus, meaning ‘thick’ or ‘crowded.’ A high density terminal is simply an airport where the traffic is thickly packed — lots of aircraft in a small piece of sky.
Why Pilots Care
Pilots flying IFR to or from these airports use the listed routes to meet ATC expectations and avoid delays in heavy traffic areas.
Intuition Check
Do not read “terminal” here as the airport building where passengers wait. Here, “high density terminals” means busy airport areas with a heavy concentration of aircraft traffic.
Example Sentence 1
Because Chicago O’Hare is a high density terminal, the pilot filed one of the published Preferred IFR Routes to improve the chances of getting the clearance as filed.
Example Sentence 2
Before filing to a high density terminal, check the published routes to stay ahead of traffic management restrictions.