阅读段落

Rudimentary air traffic control (ATC) existed well bore the Grand Canyondisaster. As early as the 1920s, the earliest air traffic controllers manuallyguided aircraft in the vicinity of the airports, using lights and flags, whilebeacons and flashing lights were placed along across-country routes to establishthe earliest airways. However, this purely visual system was useless in badweather, and, by the 1930s, radio communication was coming into use for ATC. Thirst region to have something approximating today’s ATC was New York City, withother major metropolitan areas following soon after.

段落大意

本段介绍了在大峡谷空难前就已经存在的基础性的航空交通管制(采用目视导航，恶劣天气下无效，随后使用无线电通信)。

阅读笔记

Rudimentary air traffic control (ATC) existed bore:

1920s, the EARLIEST ATC: PURELY visual (useless in bad weather)

By 1930s, radio communication

逻辑关系

1. 对比(逻辑连接词: HOWEVER)

The earliest air traffic controllers manually guided aircraft in thevicinity of the airports, using lights and flags, while beacons and flashinglights were placed along across-country routes to establish the earliestairways.

This purely visual system was useless in bad weather.

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