Mass murderer Jack Gilbert Graham was executed on January 11, 1957, after he used a dynamite time-bomb to blow up a plane mid-flight.

Graham wanted to murder his mother to claim tens of thousands of dollars in life insurance.

So the US man placed a time-bomb in her luggage on a flight from Colorado to Oregon on November 1, 1955.

Jack Gilbert Graham killed 42 other people in an effort to kill his mother. (FBI)

The crash killed his mother and the other 43 people on board instantly.

Within a few days, investigators concluded there must have been a mid-air explosion.

They then began a painstaking process of finding the person responsible by sorting through luggage scattered over a wide area.

Inside the handbag of Daisie King was a series of newspaper clippings about her family, including her son Graham.

Among the clippings was a newspaper story about Graham being charged with forgery.

Also drawing suspicion was the fact none of her luggage had survived the explosion.

While other bags were intact or damaged, hers had been completely destroyed.

The wreckage was strewn over a vast swath of land, with the plane’s tail seen at the bottom right of this picture. (FBI)

It was soon found that Graham had placed a travel insurance policy on the life of his mother worth $37,500.

Graham signed a confession after the FBI threatened to prosecute his wife for giving inconsistent statements.

He admitted to blowing up the plane using 25 sticks of dynamite, an immense amount for the task.

He was charged with murder after it was realised there was not a law against bombing an aircraft.

Psychiatrists were shocked by his blase attitude towards the deaths of the others aboard the flight.

“The number of people to be killed made no difference to me; it could have been a thousand,” he said.

“When their time comes, there is nothing they can do about it.”

The mass murder was committed merely as an act of insurance fraud. (FBI)

He initially pleaded not guilty for reason of insanity, then changed it to just not guilty.

But the jurors were not impressed with his defence.

It took just 69 minutes of deliberation before he was found guilty.

He was unrepentant as he was led into the gas chamber.

“As far as feeling remorse for those people, I don’t. I can’t help it. Everybody pays their way and takes their chances. That’s just the way it goes,” he said.