China Southwest Airlines Flight 4509 (SZ4509) was a flight from Chengdu Shuangliu International Airport, Sichuan to Wenzhou Yongqiang Airport, Zhejiang. On February 24, 1999 it crashed into a field while on approach to Wenzhou Airport, killing all 61 passengers and crew members on board. Witnesses saw the plane nose dive into the ground from an altitude of 2,300 feet and explode.