相关题目
The vertical separation minimum should be 300m at the altitude of or below （ ） .
Larger separations than the specified minima should be applied whenever in （ ） .
Air navigation services include （ ） .
（ ） is a circle on the surface of the earth, the plane of which passes though the centre of the earth.
（ ） is air traffic control service for controlled flights in control areas.
（ ） is a service provided for the purpose of giving advice and information useful for the safe and efficient conduct of flights.
（ ） is a service provided to notify appropriate organizations regarding aircraft in need of search and rescue aid, and assist such organizations as required.
Air traffic control service for arriving and departing controlled flights. It is （ ） .
Air traffic services include （ ） and （ ） services.
Visibility is the ability as determined by atmospheric conditions and expressed in unit （ ） .
