To enter Class B airspace, such as an approach to a major metropolitan airport, an explicit ATC clearance is required.

需要持有明确的空中交通管制许可才能进入B类空域，如接近一个大都会机场。

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Get clearance before making major design changes.

在进行主要的设计变更之前进行清理。

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We decide the cross and span clearance by over-voltage times and electrical insulation strength (air spacing) from the system major in places that the public not easy to arrive.

再根据系统确定的操作过电压倍数及电气绝缘强度（空气间隙）来确定在人不宜到达地方的交叉跨越距离；

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With its sales in the atomic-power sector falling by a third since the Fukushima accident, India "would be a major focus of business if regulatory clearance is given by the government, " a spokesman said.

WSJ: Japan, India to Restart Nuclear-Energy Talks

Shumlin, after meeting with Marois on Monday in Montreal, said a major impediment to improved rail communication remains the pre-clearance of passengers and cargo by customs officials from both countries when crossing the border.

WSJ: Vt., Quebec discuss rail link, traffic, energy

The chief executive of a major maker of DNA sequencing technology is talking about getting regulatory clearance to use his technology for medical purposes.

FORBES: Can A DNA Sequencer Get FDA Approval?