With still no trace of the missing Malaysian Airlines flight MH370, the search operation in the southern Indian Ocean is moving to a new phase, which calls for enhanced global cooperation.

Malaysia Airlines Chief Executive Officer Ahmad Jauhari Yahya said in a statement released here Thursday the continuing search and investigation would be a prolonged process and the company was adjusting the mode of services and support.

The whereabouts of Flight MH370 remain a mystery. However, the search for the ill-fated plane will continue into the future.

The sudden loss of MH370's communications with the ground left the world clueless, making it very difficult to pinpoint the location of wreckage.

But all the countries concerned have pledged maximum support for the search and rescue mission, deploying advanced vessels and aircraft and even redirecting satellites in a bid to capture useful images.

Innovative analysis of the "handshake" between the airplane and a ground station led investigators to believe the plane crashed in a remote part of the southern Indian Ocean, causing initial search efforts in the South China Sea and Malacca Strait to be moved further south.

Following Australia, New Zealand and the United States, China, Japan and South Korea also sent their military aircraft to the Indian Ocean.

The unprecedented hunt involved Russian-made IL-76 planes and Orion aircraft, British Royal Navy submarine HMS Tireless and Chinese warship Jinggangshan.

In addition to the air and surface search, the Indian Ocean search also went underwater, with the autonomous underwater vehicle, Bluefin-21, deployed to scour the sea floor.

Australian Prime Minister Tony Abbott said in a recent press conference that since MH370 went missing, more than 4.5 million square km of ocean had been searched, and 334 search flights had been conducted, an average of eight a day for a total of more than 3,000 hours.

The search has involved 10 civil aircraft and 19 military aircraft from Australia, New Zealand, the United States, China, Japan and South Korea. Up to 14 ships from Australia, China and Britain have been used to cover the search areas during the search period, he said.

And the prime minister said that, so far, each country involved in the search had been bearing its own costs.

The search is still going on in vain, though its scale is unprecedented. It shows the limits of human knowledge and how powerless we are in the face of Mother Nature.

Since the search is probably the most difficult in human history, as Abbott said, the international community has no choice but to strengthen its cooperation in order to solve the mystery.