Although the pilots had totaled up the take-off weight of the aircraft before the flight and determined it to be within limits, the plane was actually overloaded and out of balance, due to the use of incorrect (but
FAA approved) passenger weight estimates. When checked, the NTSB found that the estimates were over 20 pounds (9kg) lighter than the actual weight of an average passenger. After checking the actual weight of baggage retrieved from the crash site, and passengers (based on information from next-of-kin and the medical examiner), it was found that the aircraft was actually 600 pounds (272Kg) above its maximum allowable take-off weight, with its center of gravity 5% rear of allowable limits.
It was determined that neither problem alone would have caused the loss of control, which explains why it departed Huntington, West Virginia safely.
Aftermath
As a result of the weight issues discovered, the FAA planned to investigate and potentially revise estimated weight values, something that was not done since 1936. Air Midwest now use an average weight of 200 pounds(90.7Kg) per passenger, but the NTSB suggests that airlines use actual weights instead of average. 70% of small air carriers still use average.
[4] Air Midwest publicly apologized for the incident after the family of crash victim Christiana Grace Shepherd pressured the airline to do so.