Engine Anti-Icing

The pilot apparently decided not to return to the gate for reapplication of deicing, fearing that the flight's departure would be even further delayed. More snow and ice accumulated on the wings during that period, and the crew was aware of that fact when they decided to make the takeoff.
The crew did not activate the engine anti-ice system. The copilot announced and the pilot confirmed that the plane's own engine anti-icing system was turned off.
First Officer Pettit noted several times to Captain Wheaton that the instrument panel readings he was seeing did not seem to reflect reality (he was referring to the fact that the plane did not appear to have developed as much power as it needed for takeoff, despite the instruments indicating otherwise). The captain dismissed these concerns and let the takeoff proceed. Investigators later determined that there was plenty of time and space on the runway for Wheaton to have aborted the takeoff, and criticized his refusal to listen to his first officer, who was correct that the instrument panel readings were wrong. The pilot was told not to delay because another aircraft was 2.5 miles out (4 km) on final
approach to the same runway.
Pilot error, the National Transportation Safety Board determines that the probable cause of this accident was the flight crew's failure to use engine anti-ice during ground operation and takeoff, their decision to take off with snow/ice on the airfoil surfaces of the aircraft, and the captain's failure to reject the takeoff during the early stage when his attention was called to anomalous engine instrument readings.
Contributing to the accident were the prolonged ground delay between deicing and the receipt of ATC takeoff clearance during which the airplane was exposed to continual precipitation, the known inherent pitch up characteristics of the B-737 aircraft when the leading edge is contaminated with even small amounts of snow or ice, and the limited experience of the flight crew in jet transport winter
operations.
The error chain (Class 3) began with the pilot instructed deicing on the plane and no covers or plugs installed over engines or airframe openings during the operation by maintenance personnel. Also, flight was delayed due to bad weather thus increasing the stress of pilot and first officer (Physiology, Class 4). This affects the decision making of the pilot and first officer throughout the flight operation; the pilot’s decision to abort the takeoff in preventing further delay (Decision Making, Class 1). The pilot and first officer did not think of the consequences if they use of reverse thrust on the ground to push back and positioning aircraft near the exhaust from the preceding DC-9’s engines to melt the snow off the wings (Hazardous attitude: Impulsiveness, Class 1). First officer saw a problem with the instrumentation but the captain shrugged off his concerns. The captain was sure everything was in order and he displayed a (Lack of Leadership with Respect, Class 1/Hazardous Attitude: Machosim, Class 1). The "non-assertive" co-pilot and crews were afraid to express concern due to the role of the "domineering" captain (Personality, Class 1).