Two US Marine Corps helicopters on a night time training mission have crashed into the waters of the Gulf of Aden, leaving two crew members injured and 10 others missing. The CH-53 helicopters went down around 5.30pm local time on Friday in the waters near Ras Siyuan in northern Djibouti, a US military statement said. "There were a total of 12 crew members aboard at the time of the crash," the statement said. "Djiboutian military members near the impact site responded immediately and were able to rescue two injured crew members," it said.