Boeing 737 N477AS incident near Seattle, Washington

Probable cause

the flight crew's misidentification of the taxiway as the landing runway.

NTSB analysis

The flight crew inadvertently landed on a taxiway that ran parallel to the intended landing runway. About 5 miles from the runway and having been cleared to land on runway 16R, the tower controller asked if the flight would like to sidestep to runway 16C which had recently opened. The flight crew accepted and visually lined up with taxiway T, instead of the intended landing runway 16C. Although visual meteorological conditions were present, the sun was reflecting off taxiway T resulting in the flight crew visually focusing on it during landing. The flight crew and controller did not recognize the error until after landing.

Text from the NTSB. Open the NTSB docket for DCA16IA036 for the full record.