Seven months after a titanium blade snapped inside the engine of a Southwest Airlines jet, causing an emergency landing in Philadelphia and the death of one passenger, a federal investigation has zeroed in on two central questions:

Why did the blade break? And why weren't its shards contained by a protective sheath that surrounded the engine, preventing further damage to the plane?

Read more: http://www2.philly.com/philly/health/science/southwest-flight-1380-engine-blade-ntsb-20181120.html