A direct chartered cargo flight was made by China Airlines from Taiwan Taoyuan International Airport to Chengdu Shuangliu International Airport sending some 100 tons of relief supplies donated by the Tzu Chi Foundation and the Red Cross Society of Taiwan to the affected areas. Approval from mainland Chinese authorities was sought, and the chartered flight departed Taipei at 17:00 CST, May 15 and arrived in Chengdu by 20:30 CST. A rescue team from the Red Cross in Taiwan was also scheduled to depart Taipei on a Mandarin Airlines direct chartered flight to Chengdu at 15:00 CST on May 16.
Try to answer this question if possible (otherwise reply "unanswerable"): What date did the cargo flight leave?
May 15