AIM Text
A warning area is airspace of defined dimensions, extending from three nautical miles outward from the coast of the U.S., that contains activity that may be hazardous to nonparticipating aircraft. The purpose of such warning areas is to warn nonparticipating pilots of the potential danger. A warning area may be located over domestic or international waters or both.
Source: FAA Aeronautical Information Manual · current edition · paragraph 3-4-4.
The short answer
This AIM section explains FAA advisory guidance on warning areas: airspace of defined dimensions extending from three nautical miles outward from the U.S. coast that contains activity which may be hazardous to nonparticipating aircraft. Its purpose is to warn nonparticipating pilots of potential danger. A warning area may lie over domestic or international waters, or both.
Research Notes
Common Questions
How far offshore does a warning area begin?
Per this AIM guidance, a warning area is airspace of defined dimensions extending from three nautical miles outward from the coast of the U.S. It may be located over domestic or international waters, or both.
Why does the FAA establish warning areas?
The purpose is to warn nonparticipating pilots of the potential danger from activity that may be hazardous to nonparticipating aircraft. The AIM frames this as advisory notice rather than an outright flight prohibition.
Can a warning area be over international waters?
Yes. According to the AIM, a warning area may be located over domestic or international waters or both, because it begins three nautical miles outward from the U.S. coast.