Spacing of aircraft while landing and taking off at airports to achieve safe and orderly movement in flight.

Wildfire caused directly or indirectly by lightning.

Fire caused by mechanical equipment other than railroad operations.

Foam intended for use on Class A or woody fuels; made from hydrocarbon-based surfactant, therefore lacking the strong filming properties of Class B foam, but possessing excellent wetting properties.

Spinning vortex column of ascending hot air and gases rising from a fire and carrying aloft smoke, debris, and flame. Fire whirls range in size from less than one foot to over 500 feet in diameter. Large fire whirls have the intensity of a small tornado.

Specially trained and equipped fire crew for initial attack on a fire.

An application of fire danger rating to support regulation of contractors involved in land management activities for fire prevention purposes in California.

Communication call sign assigned as a unique identifier to an aircraft.

Fire crew member in the progressive method of line construction who cuts and clears away brush, small saplings, vines, and other obstructions in the path of the fireline; usually equipped with ax or brush hook, or pulaski.

A search technique typically dividing into squares the specific origin area and ignition area of a wildland fire to systematically search for microscale fire pattern indicators and evidence.