Sgt. Hamish Paterson/Commonwealth of Australia, Department of Defence
2014: Malaysia Airlines Flight 370 disappears over the Gulf of Thailand while flying from Kuala Lumpur to Beijing, China. The aircraft is believed to have crashed into the Indian Ocean off the coast of Australia, killing all 239 people on board. Despite a multinational search effort that became the largest and most expensive in aviation history, no confirmed flight debris has been found and it remains unknown what caused the disappearance.