空中警戒是最薄弱的一环。
一名声称自己儿子随一个氦气球漂浮在空中并因此引发公众警戒的美国男子被判刑90天监禁，他妻子获刑20天。
US man who triggered a major alert by falsely claiming his son was adrift in a helium balloon has been sentenced to 90 days in jail - and his wife to 20.
预警机具有低空目标警戒和空中作战指挥能力，在现代战争中占有极其重要的地位。
The early waring airplane(EWA) is a special type of airplane which has ability to monitor targets in lower attitude and to control air fighting , so that it plays an important role in modern war.
美国航空航天局计划在周二发射演示火箭，但是计划被肯尼迪太空中心上空密布的云层和一艘在发射警戒区域四处游逛的船所打乱。
NASA planned to launch the demo rocket on Tuesday but was stymied by cloudy skies over the Kennedy Space Center and by a boat that wandered into the launch danger zone.
随着空中交通流量的日益上升，空中交通警戒和防撞系统(TCAS)在保障飞行安全方面的作用越发重要。
Traffic Alert and Collision Avoidance System (TCAS) plays a more and more important role in flight safety with the constantly increasing air traffic flow.
随着空中交通流量的日益上升，空中交通警戒和防撞系统(TCAS)在保障飞行安全方面的作用越发重要。
Traffic Alert and Collision Avoidance System (TCAS) plays a more and more important role in flight safety with the constantly increasing air traffic flow.
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