HISTORY OF FLIGHT On October 30, 2006, Alaska Airlines flight 61, a Boeing 737, N740AS, took off from runway 34R instead of runway 34C (center), which was the assigned runway, at Seattle-Tacoma International Airport, Seattle, Washington. None of the 5 crewmembers and the 71 passengers was injured, and the airplane was not damaged. The airplane, which was operating under the provisions of 14 Code of Federal Regulations Part 121, continued uneventfully to its destination of Juneau International Airport, Juneau, Alaska. According to the captain of the flight, there was a short delay at the gate because of "a cargo issue." As a result, the flight crew had to correct the flight paperwork and obtain an amended release from dispatch. While at the gate, the first officer (FO) of the flight obtained the automatic terminal information service (ATIS) information "Golf" and received the flight's air traffic control clearance via the aircraft communications addressing and reporting system. ATIS "Golf" indicated that both full-length and taxiway Q intersection takeoff operations were being conducted from runway 34R. According to the flight crewmembers, during the delay at the gate, they performed a taxi briefing, which included a departure briefing from runway 34R. After pushback from the gate, the ground controller instructed the flight to follow another airplane to runway 34R at taxiway Q. The captain stated that he was taxiing slowly to allow time for dispatch to send the amended release. During the "short taxi," the captain handled the radios, and the FO worked with dispatch to complete the flight paperwork. As the flight approached taxiway Q, the FO received the amended release. The captain then switched over to the tower frequency and heard the local controller (LC) instruct the flight to taxi the airplane into position and hold on runway 34C. The captain stated that, even though he read back "34 center" to the controller, he was still thinking that the airplane would be taking off from runway 34R. During this time, the FO was completing the preflight activities. The LC then issued the flight takeoff clearance from runway 34C and indicated that there was traffic on short final. The captain stated that he "was sure the tower controller said runway 34C" and "read back what he heard" but that he "was thinking runway 34R." As the airplane taxied onto the centerline, the captain conducted a compass check and then transferred control of the airplane to the FO. The airplane departed uneventfully from runway 34R. The flight crew stated that the first indication that the airplane had departed from the wrong runway was when the controller informed them after takeoff. According to the local controller, he was scanning the runways and noticed that the airplane was rolling on runway 34R abeam the tower instead of runway 34C. Because there were no potential air traffic conflicts at the time, the controller thought that it would be safer to let the airplane depart from runway 34R than to have the pilots abort the takeoff. AIRPORT INFORMATION Seattle-Tacoma International Airport (SEA) has two operational runways, 16L/34R and 16C/34C. Runway 16R/34L is currently under construction. Runway 16L/34R is 11,901 feet long and 150 ft. wide. Runway 16L/34R is 9,426 feet long and 150 feet wide. Runway 34R has 9,426 feet remaining from intersection Q.