Fireflies give off flashes of light when they fly at night.

萤火虫夜间飞行时发出闪光。

《新英汉大辞典》

Many fly at night, when temperatures are cooler.

很多鸟类在温度较低的夜间飞行。

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If you are willing to fly at night, you can get a much cheaper ticket.

如果你愿意乘夜晚的航班，你就可以买到一张便宜得多的机票。

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The aircraft had the bat-wing insignia of her son's unit, the "Vampires" -- so-called because they usually fly at night.

CNN: Families of captured pilots wait, hope

Air ambulances serving Sussex, Kent and Surrey are to fly at night from early next year, creating a 24-hour service.

BBC: Air ambulances to fly at night in Sussex, Kent and Surrey

It would use solar power during the day, while recharging the batteries, which would then provide enough "juice" to fly at night.

BBC: NEWS | Science/Nature | 'Eternal planes' to watch over us