Graham plotted to take his mother’s life to secure a hefty payout from her life insurance policy, amounting to tens of thousands of dollars.

The tragic crash resulted in the immediate death of his mother along with the other 43 passengers on board.

Just a few days later, investigators determined that a mid-air explosion was the likely cause.

They embarked on a meticulous search for the culprit, combing through luggage that had been strewn across a vast area.

In Daisie King’s handbag, they discovered a collection of newspaper clippings about her family, prominently featuring her son, Graham.

Among these clippings was an article detailing Graham’s previous charge of 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.

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.”

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.