Nell Calloway(R), granddaughter of Flying Tigers commander Gen. Claire Lee Chennault, lies a wreath to commemorate U.S. aviators during a ceremony at the Air Force Memorial in the outskirt of Washington D.C. on May 28, 2012. The Flying Tigers, a U.S. volunteer group which fought alongside the Chinese against Japanese aggressors in World War II, were honored in a ceremony Monday by the Air Force on the country's Memorial Day, a day of remembrance for the men and women who died while serving in the armed forces. [Xinhua]