Definition
Airspace of defined vertical and lateral dimensions established at locations where there is a requirement for increased security of ground facilities. Pilots are requested to voluntarily avoid flight through these areas. When greater security is needed, flight may be temporarily prohibited by regulation under 14 CFR Part 99.
Plain English
A patch of airspace around a sensitive ground site where pilots are asked to stay out as a courtesy. If the situation gets more serious, the FAA can make staying out mandatory.
Context Anchor
Seen in special use airspace discussions, on aeronautical charts, and in preflight planning when checking whether a route passes near a security-sensitive location.
Derivation
Combines 'national' meaning of the country with 'security' meaning protection from threats, highlighting zones critical to overall U.S. safety.
Why Pilots Care
Overflight can trigger security concerns or temporary restrictions, requiring pilots to adjust routes during planning.
Intuition Check
Do not assume an NSA is always closed airspace. Most of the time it is a strong request to avoid the area; it becomes mandatory only when a temporary prohibition is issued.
Example Sentence 1
During preflight planning, the pilot noted a National Security Area near the route and chose a course that kept the aircraft well clear of it.
Example Sentence 2
During a VFR cross-country, the instructor pointed out the NSA near the capital and explained the avoidance request.