The final report was released by the NTSB on July 12, 2022, more than 3 years after the accident. The NTSB concluded that the probable cause of the accident was
confirmation bias which prompted the crew to continue descending even though they had not positively identified the runway. The NTSB also determined that the first officer was
fatigued, which contributed to his confirmation bias; that the captain had demonstrated "poor judgment and decision-making" in instructing the first officer to continue the approach although he did not have the runway in sight; and that the ILS localizer was out of tolerance by about to the right, a condition that had been noticed during six previous CommutAir flights, including by the accident first officer, but had not been properly reported to the FAA.
Weather Around the time of the first approach, the
Automatic Weather Observation System (AWOS) at the airport was reporting wind from 060° at and visibility of in moderate snow and freezing fog. Fourteen minutes after the accident, visibility had improved to , with scattered clouds at AGL, and an overcast ceiling at AGL. In a post crash interview, the first officer of the flight stated that when he transitioned from looking at his flight instruments to the outside, all he could see was "white on white".
Crew The NTSB identified the first officer's lack of sleep as a contributing factor. He had been recently suffering from the
flu and had lost sleep, and had made only limited and inconsistent use of his prescribed
continuous positive airway pressure machine for several days leading to the accident. He had not gone to sleep until around 1:00 EST the night before the accident due to flight and shuttle delays during the preceding workday, and he had only slept until 6:00 EST, about five hours, whereas he usually slept for about eight hours. The NTSB commented on the captain's flight training record. While she had been a
de Havilland Canada DHC-8 first officer with CommutAir, she had received a disciplinary letter and been subject to nine months of monitoring before being allowed to pursue captain upgrade training. She failed her EMB-145
checkride during her initial attempt and was later placed under "increased scrutiny" by CommutAir twice. Although she had subsequently received her EMB-145
type rating and been upgraded to captain, the NTSB said that "her repeated training problems indicated an inadequate foundation for being a captain, which CommutAir did not effectively address."
Localizer About 36 hours before the accident, a CommutAir flight crew had noticed the lateral localizer error and reported it to the Boston Air Route Traffic Control Center; however, FAA procedures dictated that before a navigational aid malfunction could be officially reported, a second independent report of the error was needed, which had not been received. Airport maintenance staff did not have the means to measure localizer alignment directly. Investigators found that the localizer antenna was surrounded by of snow; after confirming the reported localizer misalignment, the snow was cleared, and this caused correct localizer alignment to be restored. FAA guidance before the accident did not specifically address snow depth around a localizer antenna; after the accident, the guidance was revised to state that localizer alignment should be checked if snow accumulated to a depth exceeding The NTSB found that at least six CommutAir pilots had noticed the localizer misalignment within the preceding five days before the accident but none had filed a company aviation safety action program (ASAP) report; however, four of them filed ASAP reports after the accident. The CommutAir managing director of safety could not state a reason why the reports were not filed earlier. ==References==