Definition
A formal determination, issued by a federal agency such as the FAA, that a proposed action will not have a significant effect on the human or natural environment, and therefore does not require the preparation of a full Environmental Impact Statement (EIS) under the National Environmental Policy Act (NEPA).
Plain English
An official decision that a planned project — like a new runway, airport expansion, or change to flight procedures — won't harm the environment enough to require a full environmental study.
Context Anchor
Seen in airport planning, airspace changes, runway projects, and environmental review documents rather than in normal cockpit operations.
Derivation
The phrase is purely descriptive: a 'finding' (a formal conclusion reached after review) of 'no significant impact' (no meaningful environmental effect). It originates from the language of NEPA, the 1969 federal law that requires environmental review of major federal actions.
Why Pilots Care
FONSIs often appear in the public record when airports propose new runways, towers, instrument procedures, or operational changes. Pilots involved in airport advocacy, local flying clubs, or community aviation issues may encounter these documents and need to know what the term signals.
Intuition Check
Do not read “no significant impact” as “no impact at all.” It means the expected environmental effects are not large enough, under the review standard, to require a more detailed environmental impact study.
Example Sentence 1
The FAA issued a FONSI for the proposed taxiway extension, allowing the airport to proceed without a full environmental impact statement.
Example Sentence 2
With the FONSI in hand, the airport could begin construction without further environmental delays.