On a snowy January evening in 1971, three executives with Atlanta-based Cousins Properties left Vermont on a private jet after visiting an urban development site in Burlington.

Soon after takeoff, the 10-seat Rockwell 1121 Jet Commander carrying the trio, as well as the pilot and co-pilot, disappeared from radar, fueling a mystery that was solved 53 years later after a research team finally discovered the wreckage deep in Lake Champlain.

Undersea researcher Gary Kozak and his team announced that he found and created sonar images of the submerged wreckage of the private corporate jet 3 miles southwest of where the aircraft took off from Burlington, west of Juniper Island, The Associated Press reported.

While Kozak hasn't recovered any of the wreckage or the remains of the three Cousins executives who died, Robert Williams, R. Kirby Windsor and Frank Wilder, the sonar images revealed the exact color schemes of the missing jet.

“With all those pieces of evidence, we’re 99% absolutely sure,” Kozak told the AP.

Cousins is one of Atlanta’s most storied commercial real estate development firms. Founded by Tom Cousins in 1958, the firm developed iconic projects like the CNN Center, recently rebranded as The Center, in Downtown Atlanta, the 191 Peachtree Tower skyscraper and the first phase of the Georgia World Congress Center. He was at the helm of the company when the plane disappeared.

“The tragic plane accident was a very sad time for the Cousins organization,” a Cousins spokesperson told Bisnow in a statement. “We lost dear friends and colleagues. Our thoughts and prayers are with the families.”

Signs of the wreckage first appeared on Shelburne Point, just southwest of Burlington, Kozak told USA Today, months after the plane disappeared and after Lake Champlain thawed from the winter. But up until Kozak’s discovery, the jet’s main wreckage field had been elusive, despite more than 17 attempts at searching for its remains, USA Today reported.

Kozak said he found the plane’s fuselage, two turbine jet engines and a broken wing.

“I’m feeling relieved that I know where the plane is now but, unfortunately it’s opening other questions and we have to work on those now,” Frank Wilder's son, also named Frank Wilder, told the AP.

Wilder said the wreckage added more complicated questions to what happened to the Jet Commander that fateful evening.

Barbara Nikitas, whose uncle George Nikita was the pilot, told the AP the discovery brought a “peaceful feeling, at the same time it’s a very sad feeling.”

National Transportation Safety Board spokesperson Peter Knudson told USA Today the agency was uncertain what level of examination it could conduct “if and when any of that wreckage were recovered.”

“We will be evaluating the specifics of what we found and the degree of certainty to which we are able to positively link it back to the wreckage that was located,” Knudson said.