Airspace of defined dimensions extending from 3 nautical miles outward from the coast of the U.S. containing activity that may be hazardous to nonparticipating aircraft. A warning area may be located over domestic or international waters or both. Permission is not required but a flight plan is advised. e. Alert area – Depicted on aeronautical charts to inform nonparticipating pilots of areas that may contain a high volume of pilot training or an unusual type of aerial activity. No permission is required, but VFR flights should exercise extreme caution. IFR flights will be cleared through or vectored around it.