The National Transportation Safety Board determined that the cause of the accident was a pilot error due to ice on the wings. The plane had not been de-iced for a significant amount of time when the pilot chose to take off just before 4 p.m.

The crash of Air Florida Flight 90 in 1982 was caused by a fatal combination of pilot error and severe icing. The NTSB determined that the crew failed to activate the engines' internal ice protection systems during a heavy snowstorm in Washington D.C. This led to false engine power readings; the pilots thought they had full takeoff thrust when they were actually underpowered. Furthermore, the pilots attempted to use the "heat" from a DC-9 taxiing in front of them to melt ice on their wings, which actually caused the slush to freeze into a more dangerous, irregular shape on the leading edges. Despite the First Officer noting that the instrument readings seemed "wrong" during the takeoff roll, the Captain decided to continue. The plane stalled immediately after lift-off and crashed into the 14th Street Bridge and the frozen Potomac River. The tragedy led to massive industry-wide changes in Cold Weather Operations and "Crew Resource Management" (CRM) training, emphasizing that a junior pilot must speak up if they detect a critical safety error.