The Australian Transport Safety Bureau (ATSB) has defended its findings that the missing Malaysia Airlines flight MH370 was out of control when it landed, rejecting the theory that the pilot consciously crashed the aircraft.

The Boeing 777 aircraft, which went missing in March 2014 while flying from Kuala Lumpur, Malaysia, to Beijing, China, has not been discovered despite a widespread search led by Australia in the southern Indian Ocean.

A privately funded search commissioned by Malaysia to find the plane that carried 239 passengers is also underway.

The failure to find the plane has fuelled various theories that do not match with the conclusion reached by the ATSB that the plane made an out-of-control high-speed plunge into the water.

“We have quite a bit of data to tell us that the aircraft, if it was being controlled at the end, it wasn’t very successfully being controlled.”

One theory blames pilot Zaharie Ahmad Shah for deliberately landing the aircraft in a controlled way on the surface of the ocean.

This theory was backed by former Canadian air crash investigator Larry Vance in a new book. Vance has also said that the conclusions of the ATSB-led investigation are wrong.

At a parliamentary hearing in Canberra, Australia, Peter Foley, the ATSB chief technical officer who headed the MH370 search, offered a possible theory.

According to Foley, the pilot was probably unconscious in the flight’s final moments due to decompression sickness.

Foley said: “We have quite a bit of data to tell us that the aircraft, if it was being controlled at the end, it wasn’t very successfully being controlled.”

Investigators have confirmed that three pieces of debris washed up on western Indian Ocean shorelines came from MH370.