The association also said that standards of training must be raised among flight crews and air traffic controllers as the sky has become ever more crowded.

该协会还表示，必须提高机组人员和空中交通管制员的培训标准，因为空中交通越来越拥挤。

youdao

youdao

The sky began to darken as the storm approached.

暴风雨来临时天空变得黑沉沉的。

《牛津词典》

From high in the air, visitors can clearly see the third area of the park -- a high broad flat rock known as the Island in the Sky.

VOA: special.2009.04.15

The latter idea is about as blue-sky as you can get, but systemic changes are ultimately more powerful than any awareness campaign.

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Zynga has been a disaster for shareholders this year, plunging almost 80%, as sky-high valuations for social media companies on the private market have proven poor indicators of public sector performance.

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Last year there was speculation MTV could be removed from Sky's subscription package as Sky re-negotiated its deal to carry the network.

BBC: MTV Video Music Awards