A murder trial in Toronto has heard that an aviation executive was very excited about a new business venture in the weeks before he died from a single gunshot wound to the head.

The death of 71-year-old Wayne Millard on Nov. 29, 2012 was initially ruled a suicide, but in 2014, his son -- Dellen Millard -- was charged with murder in the death of his father.

Court heard that Wayne Millard had recently moved Millardair -- his family-owned aircraft servicing and maintenance company -- from Toronto's Pearson airport to Region of Waterloo International Airport, where he had built a massive hangar.

Chris Wood, the general manager of the Waterloo airport, testified today that on Nov. 1, 2012, Wayne Millard had received a crucial certification for his business from Transport Canada and was very happy.

Wood says Wayne Millard told him he was investing in Millardair because the legacy of the family company was really important to him.

Dellen Millard, a twice-convicted murderer who is serving two consecutive life sentences, has pleaded not guilty to first-degree murder.

Wood testified that Dellen Millard was not interested in running the family company, and after his father's death, he quickly fired all Millardair staff and returned the valuable government certification.

"We thought that was a poor business decision," said Wood. "If you'd like to get maximum return out of business, you sell the business with the hangar with certificate and staff in place."

Court has heard that Dellen Millard, now 32, told police his father suffered from depression, alcoholism and was under a lot of stress from the new business.

Millardair was started by Carl Millard, Wayne Millard's father, in 1963 and operated as a cargo airline, then a passenger airline, before the business shifted into renting out its hangar at Toronto's Pearson airport.

Wayne Millard took over the business when his father died in 2006.

Wood told court he approached Wayne Millard in 2009 to woo him away from Toronto. In short order they had an agreement, he said, and construction began in 2011 on a hangar that was triple the size of any other hangar at the Waterloo airport.

Wayne Millard was taking his company in a new direction to service and repair aircraft. Then, after more than a year of work, Millardair received the Transport Canada certification.

"He was very excited, very happy ... there was a lot of excitement at the airport. It was a very large hangar and a real big win to have this type of business come to our airport," Wood said.

That excitement soured after Wayne Millard died, he said. The hangar was full of "junk," he said, including old cars, a couple small planes, a helicopter and a bunch of car parts.

"It became more and more clear it was not going to be used for what it was intended," Wood said.

"We were growing increasingly frustrated that 90 jobs were promised and aircraft were going to start coming, so we ratcheted up pressure to enforce the lease."

The hangar was later sold to another company, Wood said.

Court has heard that Dellen Millard called his dad a failure and blamed him for the company's financial problems. Court documents show Dellen Millard's DNA was on the handle of the gun that was found next to Wayne Millard's body.

A shooting reconstruction expert testified Thursday that forensic testing suggested it was "unlikely" Wayne Millard shot himself.