the first officer informed the captain that the target airspeed for landing would be . This value was based on standard procedures in the Southwest Airlines Flight Operations Manual (FOM). At 18:05:13 the captain told the first officer that the air traffic controller had instructed them to remain at or greater "for a while." At 18:05:54 the controller cleared Flight 1455 to descend to , and at 1807 cleared the flight to descend to . At 1808 the controller cleared flight 1455 for a visual approach to runway 8 with a restriction to remain at or above 3,000 feet (above mean sea level) until passing the Van Nuys VOR beacon. This navigational aid is approximately from the runway. Radar data suggest that the flight began its descent from about from the runway. According to the Aeronautical Information Manual Section 4-4-12f, this approach clearance automatically canceled any previous speed assignments. According to the final accident report, traffic conditions no longer warranted the speed assignment after the controller cleared the flight to descend to , but the controller did not verbally cancel the speed assignment. Southwest Airlines procedures then in place had the non-flying pilot (pilot monitoring) make altitude call-outs at 1000, 500, 400, 300, 200, 100, 50, 30, and . Additionally, call-outs are required if certain parameters are not met, in this case flight speed and sink rate. At 1809:32, one minute and thirteen seconds after approach clearance was given, and at of altitude, the captain began to slow the aircraft by deploying the flaps. At 18:10:24 the ground proximity warning system (GPWS) began to sound a "sink rate" warning in the cockpit. The aircraft was descending at an angle of 7 degrees, when the angle of descent for most aircraft landing on that runway was 3 or 4 degrees. Both pilots ignored the warnings. At 18:10:44 the warning system in the cockpit began to sound. The captain responded to these warnings with "that's all right." The captain stated after the accident that he knew as the aircraft passed that he was not "in the slot," meaning the conditions had not been met for a safe landing, in this case because of an excessive airspeed. The captain further stated that he understood that if he was not "in the slot," procedures demanded a go-around maneuver to abort the landing. He could not explain why he did not perform a go-around maneuver.