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.

The MD-11F freighter operated by UPS, crashed after one of its engines separated from the wing as it was preparing to take off from Louisville.