Incident Details
On December 19, 2015, at approximately 0831 Pacific Standard Time, Alaska Airlines Flight 27, a Boeing 737 registered as N477AS, landed on taxiway T instead of the intended runway 16C at Seattle-Tacoma International Airport (SEA) in Seattle, Washington. The flight, operating under 14 CFR Part 121 as a regularly scheduled passenger service from Chicago O'Hare International Airport (ORD) to SEA, carried 153 passengers and crew. No injuries were reported, and the aircraft sustained no damage. Visual meteorological conditions prevailed at the time of the incident.
Crew Reports
The captain reported that the descent and approach were normal. The flight had been cleared for the instrument landing system (ILS) approach to runway 16R. Inside of 5 miles from the airport, the tower controller offered runway 16C, which had recently opened. The captain aligned the airplane to land on what he believed was runway 16C. He noted that runways 16C and 16R and taxiway T were wet and reflected the morning sun, while runways 16L and the terminal were in a shadowed area and not readily visible. He further observed that the distance from runway 16L to 16C is less than the distance between 16C and 16R, which might make 16C appear as the left runway and taxiway T as the middle runway. The captain suggested that runway lead-in lights should remain illuminated to prevent similar events in the future.
The first officer reported that both pilots were focused on landing what they thought was runway 16C, but was actually taxiway T. Although the first officer had retuned the captain's ILS for runway 16C, he was puzzled that the flightpath indicator showed on-glideslope while the localizer showed off course. He casually mentioned the discrepancy, but since they were visually aligned with what they believed was the runway, he did not pursue it further. The first officer noted that he had been overly focused on secondary tasks and neglected the big picture of ensuring the airplane was lined up on the correct runway.