Although some so-called contrails, which are simply clouds of tiny ice crystals condensed from the moisture in aircraft exhaust, evaporate quickly, many linger for hours and spread across the sky.

这些所谓的“飞行云”不过是飞机尾气中的湿气冷凝而成的云状微型冰晶颗粒，尽管其中有些会很快蒸发，但是很多会逗留数小时，并弥漫天空。

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Although some so-called contrails, which are simply clouds of tiny ice crystals condensed from the moisture in aircraft exhaust, evaporate quickly, many linger for hours and spread across the sky.

这些所谓的“飞行云”不过是飞机尾气中的湿气冷凝而成的云状微型冰晶颗粒，尽管其中有些会很快蒸发，但是很多会逗留数小时，并弥漫天空。

youdao