问题原来出在机身的金属疲劳。

The problem turned out to be metal fatigue in the fuselage.

《柯林斯英汉双解大词典》

就在几周前，飞机工程师才发现他们并没有完全了解金属疲劳——四月一日，西北航空公司812航班使用的波音737-300型客机在从凤凰城飞往萨克拉门托的途中发现在机身的上半部有一个五英尺的裂纹，不得不紧急迫降。

Over the past few weeks, aircraft engineers have found they do not know quite as much about metal fatigue as they thought.

youdao

就在几周前，飞机工程师才发现他们并没有完全了解金属疲劳——四月一日，西北航空公司812航班使用的波音737-300型客机在从凤凰城飞往萨克拉门托的途中发现在机身的上半部有一个五英尺的裂纹，不得不紧急迫降。

Over the past few weeks, aircraft engineers have found they do not know quite as much about metal fatigue as they thought.

youdao