On December 19, 2015, about 0831 pacific standard time, Alaska Airlines flight 27, a Boeing 737 airplane, N477AS, landed on taxiway T instead of the intended runway 16C at the Seattle-Tacoma International Airport (SEA), Seattle, Washington. There were no injuries to the 153 passengers and crew onboard and the airplane was not damaged. The flight was conducted under the provisions of 14 Code of Federal Regulations Part 121 as a regularly scheduled passenger flight from Chicago O'Hare International Airport (ORD), Chicago, Illinois, to SEA. Visual meteorological conditions prevailed at the time of the incident.

The captain reported that the descent and approach were normal. They had been cleared for the instrument landing system (ILS) approach to runway 16R. Just inside of 5 miles, the tower controller offered runway 16C that had recently opened. The captain lined up the airplane to land on what he believed was 16C. He noted that runways 16C and 16R and taxiway T were wet and reflected the morning sun, whereas 16L and the terminal were in a shadowed area and not readily visible. He further noted that the distance from 16L to 16C is less than the distance between 16C and 16R so it may appear that 16C is the left runway with taxiway T being the middle runway. The captain suggested that runway lead-in lights should remain on to prevent future similar events.

The first officer reported that both pilots were focused on landing what they thought was runway 16C, but was taxiway T. Although the first officer had retuned the captain's ILS for 16C, he was puzzled that the flightpath indicator showed on-glideslope while the localizer showed off course. Although he casually mentioned the discrepancy, since they were visually aligned with the runway, he did not give it further attention. The first officer noted that he had been focused too much on secondary tasks and neglected the big picture of ensuring the airplane was lined up on the proper runway.