Two of the fastest and longest-range commercial jets in the country are boosting what is believed to be the largest multinational search mission in Australian history to find the missing Malaysia Airlines flight MH370.

The luxury business jets, with top speeds of 950km/h and ranges up to 12,000 kilometres, will increase the ability of a coalition of nations that includes China, Britain and Japan to scour the southern Indian Ocean for wreckage from the airliner that disappeared without a trace two weeks ago.

The jets, a Bombardier Global Express and a Gulfstream G5, are carrying emergency service volunteers as spotters.

Chartered out of Perth Airport by the Australian Maritime Safety Authority, they took the total number of aircraft searching on Saturday to six, adding to three P3-Orions from Australia and one from New Zealand.

The move came as support poured in from around the world to help the search in the remote seas 2500 kilometres off the coast of Western Australia where two large objects were spotted in the sea on satellite images last week.

The images of those objects, which may turn out to be unrelated debris, remain the only lead so far in finding the plane.

Acting Prime Minister Warren Truss said on Saturday the Australian search effort had so far covered some 500,000 square kilometres and there had been 15 flights from the RAAF base near Perth, with mainly Australian and New Zealand Orion aircraft.

Mr Truss said it was an ''intensive operation''.

''While these aircraft are equipped with very advanced technology, much of this search is actually visual,'' he said. Mr Truss said the search for debris would keep going as long as there was hope.

''It is important from the perspective of those who have families, whose whereabouts are unknown … and indeed for the future of the aviation industry, that we do whatever we can to firstly confirm whether or not the sightings as a result of the satellite imagery are indeed connected in any way with the Malaysia Airlines flight,'' he said.

Malaysian Defence and Transport Minister Hishammuddin Hussein said on Saturday Britain would send a naval hydrographic survey ship, the Echo, and that Japan would send two more Orions.

The Chinese government has also announced it would send up to seven warships and a research vessel, the Chinese icebreaker Snow Dragon, which was berthed at Fremantle.

It is due to reach the area on Sunday.

Two Chinese aircraft and two Japanese aircraft are also due to arrive in Perth on Sunday. The workhorse Orion aircraft, which can fly 100-200 metres above the water, are designed for search and surveillance, and for detecting submarines.

Each plane is equipped with multi-mode radar, which can switch from a wide beam capable of covering a large area, to a more focused area to provide higher resolution images.

On board are six analysts reviewing the images as well as providing visual surveillance.

The aircraft also have infrared and acoustic sensors that can pick up the ping from the plane's black box flight recorder. But it is likely they would need to be virtually overhead to hear them, said Dr Andrew Davies, from the Australian Strategic Policy Institute.

Bolstering the search is a P-8 Poseidon aircraft from the United States. The more modern jet aircraft is based on the Boeing 737 airframe, and is capable of searching for up to nine hours.

US journalists on board said their mobile phones and cameras were confiscated for the flight because of the top secret nature of the surveillance gear on board.

The first Orion in the area dropped buoys that will enable the planes to collect data on the currents in the area.

The satellite pictures are already a week old, so understanding the effects of currents, and where they might have moved the objects sighted, will be vital.

Also in the search areas is the MV Hoegh St Petersburg, a Norwegian car carrier that was marshalled en route to Melbourne. Its radar and powerful lights will enable it to search at night.

Any retrieval of debris will involve the HMAS Success, the largest ship built in Australia for the Royal Australian Navy, which was due to arrive at the search area late on Saturday afternoon.

Designed as a refuelling and resupply ship, the HMAS Success is able to remain at sea for long periods.

With AAP