Martin, a pilot for PSA Airlines, was taken into custody at Louisville International Airport on three counts of murder, as well as counts of arson, burglary and tampering with physical evidence.
"There will be many steps from here," Beshear told reporters. But, he added, the indictment illustrates what can happen "when you never stop seeking justice, when you never give up on a case."
American Airlines said in a statement that it was "deeply saddened" to learn about the allegations against Martin, who has been a pilot for PSA Airlines since January 2018. The airline said that he underwent a background check and "recurrent vetting" but that there was no "criminal history that would disqualify him from being a commercial pilot."
After the indictment, American Airlines said Martin has been placed on administrative suspension pending the outcome of the case.
"We have an unwavering commitment to the safety and security of our customers and team members, and we will provide any investigative assistance possible to law enforcement throughout their investigation," according to the statement.
In November 2015, Calvin Phillips was found dead of an apparent gunshot wound in his cellar in Pembroke, which is not far from the Tennessee border, police said. His wife, Pamela, and a neighbour, Dansereau, were discovered dead in a nearby field inside Pamela's car, which had been burned, according to AP.
Authorities have not released a motive, but the radio station WKDZ-FM reported last year that Calvin Phillips was a potential witness in a previous case against Martin.
The victims' families said in a joint statement that the three were "brutally extinguished - beyond recognition from family."
"Every day, we are haunted by what was done to them and haunted further that someone was still free to do as they wish, beyond the civility of mankind or laws of our nation," they said. "We are overwhelmed with this positive step towards resolution for people we love dearly; Cal and Pam Phillips and Ed Dansereau, and the hundreds of friends, family, neighbours, co-workers and others deeply affected by their brutal end.
"We look forward to justice in court, and we look forward to a verdict to bring an end to this terror, and a fresh start at healing."
Beshear said he agreed to appoint a special prosecutor a couple year ago after the Phillips' son, Matt, told him that he was concerned that the murder investigation was not moving forward. Beshear said he assured the family members that "we're going to do everything we can to help you."
In the airport, the mood was tense and passengers were confused.
Wise's daughter, Ashley Martin (no relation to the suspect), called it "startling."
"It's scary to think this happened so long ago, and they're just now getting around to catching the guy," she told the station.
"I was definitely stressed," she added. "I felt like it was a little chaotic and unorganized. The workers ... you could tell they were stressed. You could feel that energy. You could feel the tension from flight attendants."
Martin, who lives in North Carolina, is being held without bond at the Christian County Detention Centre in Kentucky, where he is awaiting trial. A trial date has not been set.
