PERTH, April 4 -- A Chinese IL-76 aircraft took off from Perth International Airport early Friday morning to spearhead in an international joint search in Southern Indian Ocean, as Australian and Malaysian government heads promised to spare no efforts to hunt Malaysia Airlines flight 370.

The four-engined airlifter will comb an area of 5,800 square km which is 2,400 km west to Perth with thunder rains in the search area, sources with China's diplomatic missions to Australia told Xinhua.

On the 28th day of the flight's missing, three more civil aircraft have been mobilized to join in the joint search effort with a total of 14 planes, nine ships and at least one submarine planning to scour a search area of about 217,000 square km about 1, 700 km northwest of Perth which was determined by the Australian Maritime Safety Authority.

Angus Houston, chief of the Joint Agency Coordination Center ( JACC) which oversees the search effort, said at a press conference held on Friday in Perth that Royal Australian Navy commenced sub- surface search on Friday for pinger of the missing plane's flight recorder, or black box.

According to the JACC, a total of 26 State Emergency Service volunteers from Western Australia, New South Wales and Victoria will work as air observers on the three new civil aircraft. Houston said Australian is sending a new ship HMAS Perth to assist the search and will arrive in the search area in about four days.

Australian Prime Minister Tony Abbott said "it is the most difficult search in human history" after touring RAAF Base Pearce with his Malaysian counterpart Najib Razak on Thursday, and promised to spare no effort until done everything humanly can.

So far there has been zero findings related to the Boeing 777 plane carrying 239 people on board from Kuala Lumpur to Beijing after four weeks' hunt stretching from waters off Vietnam in South China Sea to a remote maritime area in Southern Indian Ocean.

As of Friday, aircraft and vessels from China, Australia, New Zealand, Malaysia, Japan, Korea, the U.S. and the U.K. have taken part in the joint search lead by Australian. But Malaysia is responsible to take the lead in the investigation of the tragedy in accordance with the Convention on International Civil Aviation.