What happened
On the date of the accident, Alaska Airlines Flight 1866, a Boeing 727, was operating a scheduled passenger service through several Alaskan cities including Anchorage, Cordova, Yakutat, Juneau, and Sitka. After departing Yakutat with 104 passengers and seven crew members, the aircraft was navigating under IFR conditions. During the flight, air traffic controllers issued various altitude and clearance changes, including instructions to maintain specific altitudes while managing other traffic, such as a Piper Apache, registration N799Y.
As the flight progressed toward Juneau, the pilot was cleared for a straight-in LDA approach, with instructions to cross the Howard Intersection at or below 9,000 feet. The captain acknowledged the descent and later reported descending through 5,500 feet and 4,500 feet. After establishing contact with Juneau Tower, no further communication was received from the aircraft.
The Boeing 727 subsequently struck the eastern slope of a canyon within the Chilkat Range of the Tongass National Forest at an elevation of 2,475 feet. The impact caused the aircraft to disintegrate, and there were 111 fatalities.
Findings
Investigations determined that the crash was caused by a display of misleading navigational information regarding the aircraft's position along the localizer course. This error led to a premature descent below the minimum altitude required for obstacle clearance. While the specific source of the incorrect information could not be identified, it was noted that the crew did not utilize all available navigational aids to verify their progress along the localizer, nor did they perform the necessary audio identification of the relevant navigational facilities.