altitude: The distance that something is above the ground or the level of the sea.
communications: Messages and information sent by telephone, television, radio, or computer.
compasses: Small tools used to show and fi nd directions.
Global Positioning System (GPS): Small hand-held units that use signals from satellites in space to fi nd locations on Earth.
hostile: Unfriendly or dangerous.
hover: To stay in one place; to fl y above one spot.
initial: First, or at the beginning.
mechanic: A person who repairs machines.
military: The Army, Navy, Air Force, Marine Corps, or Coast Guard.
mountaineering: Climbing or exploring mountains.
navigating: Using maps, compasses, the stars, or other equipment to find the way.
oxygen: A gas that makes up 20 percent of the air on Earth; people need oxygen to live.
propeller: Two or more blades that spin around a center point; on an airplane, the propeller spins to make the airplane move.
reflexes: Actions people’s bodies make automatically or on purpose; blinking is an automatic refl ex to bright light; putting one’s hands out to stop a fall is a refl ex done on purpose.
rotor: On a helicopter, the spinning blades on top and at the rear.
Royal Air Force: The air force of Great Britain.
SAR: An abbreviation for search and rescue.
survival: Staying alive.
unconscious: Not awake or aware.
Vietnam: A country in Southeast Asia; the United States fought a war there from 1963 to 1975.