The author of a book on the missing flight MH370 claims the plane was shot down by the US Air Force in a doomed bid to seize electronic equipment bound for China.

The Boeing 777 vanished in 2014 with the loss of all 239 passengers on board. Its disappearance has become one of the greatest mysteries in modern aviation and has sparked dozens of conspiracy theories.

Now, a French investigative journalist believes she has solved the puzzle.

Florence de Changy, who has been investigating and reporting on the MH370 for many years, argues that the American military used signal jamming technology to wipe the plane from radar screens – before shooting it down after a failed attempt to re-direct it.

She argues the US sought to seize sensitive electronic gear on its way to Beijing, as The Daily Mail reports.

A Malaysia Airlines plane on the tarmac at Kuala Lumpur International Airport in Sepang on July 21, 2014 (
Image:
AFP/Getty Images)

De Changy makes the case in her new 400-page book 'The Disappearing Act: The Impossible Case of MH370'.

Over 14 chapters she dismisses theories already put forward, including the idea that there was a fire on board, and that the plane was hijacked.

According to de Changy's hypothesis, the US was trying to keep hold of 2.5 tonnes of its "poorly documented Motorola electronics equipment" that had not been through the correct security screening.

She writes: "The shooting down could have been a blunder, but it could have also been a last resort to stop the plane and its special cargo from falling into Chinese hands."

Earlier this year, it was reported that wreckage believed to be from flight MH370 indicated the passenger jet crashed into the sea in an uncontrolled high-speed dive.

Independent experts analysed part of a wing spoiler, and argued the damage indicated it was torn from the Malaysia Airlines Boeing 777.

A piece of debris belonging to flight MH370 is displayed during the remembrance ceremony to mark the fifth anniversary of the Malaysian Airlines plane disappearance, in Kuala Lumpur, Malaysia, on March 3 2019. (
Image:
FAZRY ISMAIL/EPA-EFE/REX/Shutterstock)
French journalist Florence de Changy (
Image:
AFP via Getty Images)

De Changy concedes that her own hypothesis is far-fetched. But she believes she is right to dismiss other theories.

She writes: "I have established that MH370 did not U-turn, did not fly over Malaysia and, to cut a long story shot, never crashed in the Southern Indian Ocean. Many more clues point to a covert interception attempt that went terribly wrong, with a fatal accident happening at 2:40 a.m. between Vietnam and China."

On one point she is absolutely certain: 'It was not possible […] for a Boeing 777 to have simply disappeared.'

The Malaysian Airlines Flight MH370 took off from Kuala Lumpur on March 8, 2014. It should have landed in Beijing later that day but instead disappeared less than an hour after take-off.

There has been no trace of the passengers or cabin crew. More than three years after the plane vanished, debris began to wash up on beaches across the Indian Ocean

The hunt for the missing jet – the most costly and far-reaching search in the history of aviation – was called off in 2018.

There are many theories, but still no conclusive answers in the search for the missing Flight MH370.