Definition
A formal designation applied to a structure, object, or condition that, due to its height, location, or characteristics, poses a risk to aircraft in flight and therefore requires marking, lighting, or charting to make pilots aware of it. The determination is made by the FAA following an aeronautical study, and the resulting requirements typically involve obstruction lighting, paint markings, and depiction on aeronautical charts.
Plain English
Something tall or in the wrong place that planes could hit, so the FAA requires it to be lit, painted, or shown on charts so pilots can see and avoid it.
Context Anchor
Seen in FAA discussions of aircraft lighting, obstruction lighting, and conditions that pilots must notice or avoid during flight.
Derivation
Hazardous comes from an older word for risk or chance. Aerial means related to the air. Navigation originally meant guiding a vessel from place to place; in aviation it means guiding an aircraft. Together, the phrase points to a risk that affects aircraft as they move through the air.
Why Pilots Care
Failure to identify and avoid these hazards can result in mid-air collisions, especially at night or in reduced visibility, directly affecting flight safety and route planning.
Grounding Statement
If something in or near the flight path could put an aircraft in danger, it may be described as hazardous to aerial navigation.
Intuition Check
Do not read this as a vague warning that something is merely inconvenient. In FAA use, it means the thing can create a real safety risk for aircraft operating in the air.
Example Sentence 1
The new 600-foot broadcast tower was determined to be hazardous to aerial navigation, so it was fitted with red obstruction lights and painted in alternating orange and white bands.
Example Sentence 2
Construction of a new wind turbine prompted a NOTAM declaring it hazardous to aerial navigation until lighting was installed.