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。

youdao

They correspond roughly to small municipal, medium-sized metropolitan and major metropolitan airports respectively, and encompass an increasingly rigorous set of regulations.

它们分别大致相当于小型市政机场、中型都市机场和大型都市机场，并包含一套日益严格的规章制度。

youdao

The first region to have something approximating today's ATC was New York City, with other major metropolitan areas following soon after.

第一个出现类似现在的航空交通管制的地方是纽约市，很快，其它大城市也开始效仿。

youdao

In March of two thousand five, the Metropolitan Museum in New York had a major exhibit of her work.

VOA: special.2009.08.09

Well, like in any other major metropolitan city, you have buses, cable cars, cabs,

像其它一些大都市，你可以乘坐公共汽车，有线缆车，出租车，

旧金山的公共交通 - SpeakingMax英语口语达人

So what do these trends tell us about the demographic evolution of our major metropolitan areas?

FORBES: America's Fastest- and Slowest-Growing Cities

Staging really isn't something you can avoid, at least if you live in a major metropolitan area.

WSJ: How Much Staging Is Too Much?--WSJ House Talk

"There is a limited retail infrastructure once you get away from major metropolitan areas, " Mr. Goings said.

WSJ: Indonesia Provides a Tasty Dish for Tupperware