Air Midwest Flight 5481. 21 fatalities. Poor maintenance combined with overloaded aircraft and centre of gravity too far too the rear.
"As a result of the weight issues discovered the FAA planned to investigate and potentially revise estimated weight values, something that had not been done since 1936. Air Midwest used an average weight of 200 pounds (90.7 kg) per passenger after the accident, but the NTSB suggests that airlines use actual weights instead of average. 70% of small air carriers still use average."
