Alien abduction? Stolen by Russia? MH370 theories keep coming

Relatives of some of the Chinese passengers who were on board the missing Malaysia Airlines flight MH370 outline their demands to the airline at a news conference in Kuala Lumpur February 20, 2015. REUTERS/Olivia Harris

(This version of the March 4 story corrects profession in paragraph 14 to retired legal investigator from retired telecoms engineer)

SYDNEY (Reuters) - A year on from the disappearance of Malaysia Airlines Flight MH370, an extraordinary amount of key data remains unknown - fuelling conspiracy theories and heated online debate about one of aviation's biggest mysteries.