[1]: 2  The flight crew calculated the following takeoff speeds: At 02:00 central standard time (CST) first officer Johnston left the cockpit to close the main cargo door.

First officer Johnston told captain McCall "Cargo door's inspected, tail stand...I've removed it, sill guards are onboard.

At 02:09:49, three seconds after rotation, the main cargo door partially opened, which was indicated by the CVR recording a sudden increase in background noise.

The controller asked the crew the nature of the emergency, and first officer Johnston replied, "okay we got a cargo door open."

During the downwind leg, the main cargo door completely opened, causing the aircraft to yaw and roll uncontrollably.

A design flaw in the cargo door warning circuit prevented both the pilots and maintenance personnel from noticing this error.

[1]: 36–40 [3] The NTSB concluded that the accident was caused by the main cargo door opening and the subsequent loss of control of the aircraft.

The reason for the loss of control alone could not be determined because the simulator and wind tunnel tests were unable to verify aerodynamic movements caused by the cargo door separation and captain McCall's attempt to correct them.