A new attempt by a private ocean survey company is under way to find the wreckage of Malaysia Airlines Flight 370 nearly four years after it mysteriously disappeared.

The vanishing of the commercial aircraft as it flew from Kuala Lumpur, Malaysia to Beijing, China in March 2014 with 239 people aboard ranks as the world's greatest aviation mystery.

Only three confirmed fragments of MH370 have been found, all of them on western Indian Ocean shores, including a two-metre wing part known as a flaperon.

Australia, China, and Malaysia ended an unsuccessful $157m search in January 2017.

US-based company Ocean Infinity dispatched a search vessel this past week to look in the southern Indian Ocean for debris from the plane.

"The basis of the offer from Ocean Infinity is based on 'no cure, no fee,'" Malaysian Transport Minister Liow Tiong Lai said on Saturday, meaning payment will be made only if the company finds the wreckage.

"That means they are willing to search the area of 25,000 square kilometres pointed out by the expert group near the Australian waters. I don't want to give too much hope ... to the [next of kin]," he added.

Ocean Infinity said in a statement the search vessel Seabed Constructor, which left the South African port of Durban on Tuesday, was taking advantage of favourable weather to move towards "the vicinity of the possible search zone".

Search conditions are best during the current southern hemisphere summer before the colder months bring storm-force winds and mountainous seas.

The previous search was extremely difficult because no transmissions were received from the aircraft after its first 38 minutes of flight. Systems designed to automatically transmit the plane's position failed to work after this point, according to an Australian report.

Australian Transport Minister Barnaby Joyce told Australian Broadcasting Corp this week he didn't hold out much hope that the plane would be found.

"I can understand how Malaysians are incredibly driven by finding the wreckage," said Joyce. "I have, to be quite frank, some concerns as to whether it will be found."