但是有趣的是，其中有一些会朝西直线移动，而另外的则会曲折前行，或者甚至绕着大圈子移动。
But some, and this is interesting, move straight west while some zigzag or even move in large circles.
客机必须曲折地从一个信号站飞到下一个，而不是直线飞行；每一步上升或下降都需要得到地面的许可。
Instead of flying straight, planes must zigzag from one ground beacon to the next, and ascend and descend in steps, at each stage obtaining permission from the ground.
两点之间未必直线最短，有时迂回曲折能够更快地抵达终点。
Shortest between two points is not necessarily linear, sometimes the twists and turns to end faster.
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