Worn connecting hardware likely caused the left engine to detach from a UPS cargo plane that crashed in Louisville, Ky., the NTSB said.

New images from airport security video shows the UPS plane's left engine detach from the wing moments before the deadly crash.

In the preliminary report, the NTSB also references the 1979 crash of American Airlines Flight 191, noting that the DC-10 involved in that accident experienced a separation of the left engine and pylon assembly during takeoff. The agency highlights the event as a “similar” historical case in which the engine-pylon structure detached from the wing.