An Alaska Airlines Boeing 737-900, registration N477AS performing flight AS-27 from Chicago O'Hare,IL to Seattle,WA (USA) with 153 people on board, was on an ILS approach to runway 16R cleared to land on runway 16R, when tower offered a visual swing over to runway 16C, the crew opted to accept runway 16C but aligned with taxiway T in between runways 16R and 16C and continued for a safe landing on taxiway T at 08:31L (16:31Z), no other traffic was on taxiway T at that time. Tower, maintaining routine communication, cleared the aircraft to cross runway 16L, the crew read that clearance back after a slight hesitation and maintained routine communication, too.
Alaska Airlines confirmed their flight AS-27 landed on taxiway T on Dec 19th 2015, the occurrence is under investigation, further details can not be told due to the pending investigation.
The FAA reported, the occurrence is being investigated by the FAA.
On Feb 13th 2016 the NTSB announced that they have opened an investigation into the occurrence rated an incident. At the time of landing visual meteorologic conditions prevailed when the aircraft touched down on taxiway T instead of the intended runway 16C.
On Jun 10th 2020 the NTSB released their final report concluding the probable cause of the incident was:
the flight crew's misidentification of the taxiway as the landing runway.
The NTSB summarized the testimonies of both flight crew:
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.
http://flightaware.com/live/flight/ASA27/history/20151219/1200Z/KORD/KSEA