航向信标的作用是给着陆航空器提供（）。

Among “Distress”, “Urgency “and “Danger”, which one needs immediate assistance?

In weather report, “CB” means .

The primary principle to follow when dealing with hijacking event is （ ）.

The hijacker wants a car waiting on the runway, he will keep two passengers as （ ） .

“Glide slope” of an ILS can provide the aircraft a （ ） indication.

The localizer of an ILS can provide the （ ） of an aircraft to the runway.

When an aircraft cannot put gears down, it will need （ ） .

“Belly landing “means （ ） .

“Engine partially disintegrated” means the engine （ ） .

The maximum width of an air route is 20km and the minimum width is （ ） km.