Singapore daily Straits Times reported ICAO secretary-general Raymond Benjamin saying that until today, there is no conclusive evidence to say what exactly had happened to the plane when it fell out of radar coverage in the morning of March 8 last year.

"We don't know what exactly happened in the cockpit so we don't know if it was a security issue or a safety issue. We have never had a situation where an aircraft flew for seven hours before crashing," he was quoted saying in an exclusive interview.

"Without the aircraft wreckage, we don't know," he added.

Search efforts are still ongoing in the southern region of the Indian Ocean, lead by Australia which is the closest nation to the area where international investigators believe the Malaysia Airlines jetliner ended its flight.

On January 29 this year, Putrajaya declared that the plane was lost in an accident, and that all 238 passengers and crew are presumed dead.

While ICAO is reviewing global conventions on aviation accident recovery work following Australia's concerns of sustained high costs - the 16-month search effort is estimated to have cost US$111 million (RM421.8 million) - Benjamin believes the search will "continue for some time".

He stressed that the responsibility for the search and recovery of the plane's wreckage remains on the shoulders of Malaysia, China and Australia.

"For the moment, there is a strong will on the part of all of these parties to continue and, in particular, China and Malaysia," he said.