#plane_maximum_altitude__planemaximumaltitude__ceiling  maximum altitude at which a plane can fly (under specified conditions)
  supertype:  altitude.elevation__height  elevation especially above sea level or above the earth's surface
  subtype:  absolute_ceiling  the maximum altitude at which an air plane can maintain horizontal flight
  subtype:  combat_ceiling__service_ceiling__serviceceiling  altitude above which a plane cannot climb faster than a given rate

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