(1)
HEAVY - Aircraft with a maximum certificated take-off weight of 300,000 pounds or more.

(2)
MEDIUM - Aircraft with a maximum certificated take-off weight of less than 300,000 pounds but more than l5,500 pounds.

(3)
LIGHT - Aircraft with a maximum certificated take-off weight of 15,500 pounds or less.

AIR DEFENSE EMERGENCY - A military emergency condition declared by a designated authority. This condition exists when an attack upon the continental United States, Alaska, Canada, or United States installations in Greenland by hostile aircraft or missiles is considered probable, is imminent, or is taking place.
AIR DEFENSE IDENTIFICATION ZONE/ADIZ - The area of airspace over land or water, extending upward from the surface, within which the ready identification, the location, and the control of aircraft are required in the interest of national security.
(1)
DOMESTIC AIR DEFENSE IDENTIFICATION ZONE - An ADIZ within the United States along an international boundary of the United States.

(2)
COASTAL AIR DEFENSE IDENTIFICATION ZONE - An ADIZ over the coastal waters of the United States.

(3) DISTANT EARLY WARNING IDENTIFICATION
ZONE (DEWIZ) - An ADIZ over the coastal waters of the state of Alaska. ADIZ location and operating and flight plan requirements for civil aircraft operations are specified in Federal Air Regulations Part 99.
ADIZ location, and operating and flight plan requirements for civil aircraft operations are specified in Federal Air Regulations Part 99.
AIRFIELD (JCS, NATO) - An area prepared for the accommodation (including any buildings, installations, and equipment) of landing and take-off of aircraft.
AIRMET/WA/AIRMAN'S METEOROLOGICAL INFORMATION - In-flight weather advisories issued only to amend the area forecast concerning weather phenomena which are of operational interest to all aircraft and potentially hazardous to aircraft having limited capability because of lack of equipment, instrumentation, or pilot qualifications. AIRMETs concern weather of less severity than that covered by SIGMETs or Convective SIGMETs. AIRMETs cover moderate icing, moderate turbulence, sustained winds of 30 knots or more at the surface, widespread areas of ceilings less than 1,000 feet and/or visibility less than 3 miles, and extensive mountain obscurement. (See SIGMET, Convective SIGMET, Severe Weather Forecast Alerts, and Center Weather Advisory)
AIR NAVIGATION FACILITY - Any facility used in, available for use in, or designed for use in, aid of air navigation, including landing areas, lights, any apparatus or equipment for disseminating weather information, for signaling, for radio-directional finding, or for radio or other electrical communication, and any other structure or mechanism having a similar purpose for guiding or controlling flight in the air or the landing and take-off of aircraft. (See Navigational Aid)
AIRPORT - An area of land or water that is used or intended to be used for the landing and take-off of aircraft, and including its building and facilities, if any.