A few years ago scientists were surprised by the sight of two planes carving a hole through a cloud—which then began spewing snow.

几年前，科学家对两架飞机在云中形成一个空洞，随后开始飘雪的现象很是惊异。

youdao

A high concentration of ash ingested by a jet engine can become molten and cause engine failure, which is why planes are not allowed to fly through the cloud.

高浓度的火山灰一旦被吸入喷气发动机就会融化，并且造成引擎故障，因此喷气式飞机是不允许在火山灰云层中穿行的。

youdao