Boeing documented four prior failures of an engine mount part in 2011 but deemed it safe, only to have the same component fail on a UPS cargo plane in November, killing 15.

An aircraft that crashed in flames in Kentucky in November had a structural flaw that had been identified by Boeing on similar planes 15 years ago, according to investigators.

An engine part suspected of causing the crash of a UPS cargo plane and loss of 15 lives in Louisville in November was the subject of at least four previous failures on three separate aircraft, investi...