AIM ¶ 3-4-4 — Warning Areas

A Warning Area is special use airspace with defined dimensions that begins 3 nautical miles outward from the U.S. coast and contains activity that may be hazardous to nonparticipating aircraft. The key word is warn — these areas exist to alert pilots who are not part of the activity to the potential danger inside.

Key points to remember:

• Location: Starts 3 NM off the U.S. coast (outside the 12 NM territorial limit in many cases) and may lie over domestic or international waters, or both.
• Purpose: Warns nonparticipating pilots of potential hazards from the activity inside.
• Why over international waters? Because the U.S. cannot legally prohibit flight outside its territorial airspace, the FAA designates these areas as warning rather than restricted or prohibited.

Operationally, flight through a Warning Area is not prohibited, but it is strongly discouraged when active. Always check the chart, NOTAMs, and consider contacting the controlling agency before transiting one.