As a result, no radar record of the breakup exists-only of the metal rain that drifted down over East Texas, and eventually came into the view of air-traffic control.

结果关于航天飞机解体的情况一份雷达记录也没有——雷达只记录了那些从东德克萨斯州上空飘落，并最终进入空中交通管制范围内的金属雨。

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But delays and inefficiencies in air travel are due in large part to an outdated traffic-control system that still relies on slow, ground-based radar stations and repetitive voice communication.

不过航空运输延迟和低效的主要原因还是过时的空中交通管制——一套依靠地面控制、反应迟缓的雷达站和不断重复的语音通讯建立起来的体系。

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NextGen is the FAA's long-term plan to replace the current radar-based air-traffic-control system with one that operates using satellites and a global positioning system.

联邦航空管理局的长期规划是用凭借卫星和全球定位系统的次世代体系替换现有的依靠雷达的空中交管系统。

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Replacing outmoded radar-based air traffic control with more efficient systems has been possible for decades, but it has not happened.

FORBES: It's Time To Upgrade The Entire World's Infrastructure

Since then, there have been questions about the country's underfunded air traffic control systems, deficient radar system and the airlines' ability to cope with a surge in travelers.

NPR: Nearly 200 Feared Dead in Brazil Air Crash

It is set to replace radar in commercial aviation as the next generation of air traffic control systems come online by 2020.

BBC: The key to preventing lost planes