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The region of the atmosphere above which aircraft cannot fly.
(Aeronautics) the region of the upper atmosphere above which aircraft cannot fly
the indefinite boundary in the upper atmosphere beyond which the air is too thin for conventional aircraft to operate.
Region in which functional effects of the atmosphere on man and aircraft cease to exist.
the region in the upper part of the earth’s atmosphere where the air is too thin for aircraft to operate properly.See also: Atmosphere, Aviation