A US commercial pilot was arrested for an alleged triple murder while passengers waited to board the flight.

In an astonishing development in a 2015 cold case, Christian R Martin, a 51-year-old pilot for the American Airlines subsidiary PSA Airlines and former army helicopter pilot, was arrested on Saturday over the murders of three of his neighbours as the plane prepared for take-off in Louisville, Kentucky.

“It was like something you would totally see in a movie,” said Ashley Martin, who was waiting to board the fight according to Fox News affiliate WDRB.

“It was very tense,” Ashley Martin’s mother Frances Wise told WDRB. “I think it was very tense. You could tell the employees knew something was going on.”

A jail booking photo of Martin shows him still wearing his pilot’s uniform.

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A Missouri grand jury indicted Martin on three counts of murder, one count of arson, one count of attempted arson, burglary in the first degree and three counts of tampering with physical evidence.

He broke into his neighbours’ home in November 2015 and shot one of them, the indictment claims. He allegedly shot and killed the other two neighbours later that day. The latter two bodies were found in a charred car in a cornfield a few miles away, burned beyond recognition.

Shortly after the murders happened, Martin moved to North Carolina.

The suspect and his family deny any wrongdoing.

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“My dad is an American hero. He’s served his whole life and before this had a spotless record,” Martin’s daughter said in her statement. “We believe that he is innocent of these charges and hope that the truth will come out.”