On 23 December 1983, Korean Air Lines Flight 084 (KAL084), a McDonnell Douglas DC-10-30 performing a cargo flight, collided during its takeoff roll with SouthCentral Air Flight 59 (SCA59), a Piper PA-31-350, on runway 06L/24R (now 07L/25R) at Anchorage International Airport, as a result of the KAL084 flight crew becoming disoriented while taxiing in dense fog and attempting to take off on the wrong runway. Both aircraft were destroyed, but no fatalities resulted.
Accident
At 1215 Yukon Standard Time, Flight 59 was cleared from Anchorage to Kenai in accordance with its filed flight plan; however, clearance delivery told the pilot to expect a delay until 1244 due to the heavy fog covering the airport, so the pilot shut down the aircraft and he and his passengers deplaned temporarily. After reboarding and recontacting the tower at 1234, Flight 59 was delayed for about an hour at its parking location due to the continued dense fog, before finally requesting and receiving a taxi clearance around 1339 as visibility began to improve. SCA 59 arrived at taxiway W-3 (which connects the main east–west taxiway to the approach end of runway 6L) at 1344, holding short of runway 6L until the runway visual range (RVR) reached , the minimum required for the flight to take off.
At 1357, the Anchorage ground controller cleared Korean Air Lines Flight 084 to taxi for a departure on either runway 6R or runway 32; the flight crew chose runway 32. The flight crew's selection of runway 32 was contrary to Korean Air Lines' operating specifications, as these required a visibility of at least one-quarter mile for takeoff on runway 32 at Anchorage, while the visibility at the time was only one-eighth of a mile. (The National Transportation Safety Board [NTSB], which investigated the accident, was unable to determine why the flight crew chose runway 32 instead of runway 6R, in part because the aircraft's cockpit voice recorder (CVR) was never recovered.) The proper taxi route from the north apron (where the DC-10 was parked) to runway 32 would have involved taxiing south to the east–west taxiway, then making a right turn onto the east–west taxiway and following it to the threshold of runway 32 before turning right again onto the runway. However, the flight instead taxied southwest on taxiway W-1 to runway 6L/24R and lined up on the latter runway, facing west. The heavy fog prevented the ground controller from being able to see the flight's taxi route and impaired the KAL084 flight crew's ability to navigate around the airport; additionally, some of the lighted taxiway and runway designation signs along the flight's course were partially or fully burned out, making the signs less visually conspicuous and harder to see, and the intersections of taxiway W-1 with the east–west taxiway and with runway 6L/24R lacked signage to indicate the identity of either taxiway (the latter deficiency was rectified after the accident). The height above the ground of the DC-10's flight deck, about , exacerbated the flight crew's difficulties, as it increased the slant range from the crew's eyes to the runway and taxiway signage and pavement markings. After taxiing into position on what the KAL084 flight crew thought was runway 32, the captain expressed some uncertainty that the aircraft was on the correct runway, and briefly considered switching to runway 6R, but, reassured by his first officer's certainty that they were on runway 32, the captain reported at 1403 that Flight 084 was holding in position on runway 32, and, at 1404, the flight was cleared for takeoff. At no time did the flight crew, despite the uncertainty expressed by the captain, attempt to use their instruments to verify that the heading of the runway they were on matched that of runway 32; the NTSB was unable to determine the reason for this omission.