Harris was a fighter pilot in the Air Force and in the Air National Guard. He wasn't limited to jets; he flew cargo planes and helicopters, too, Cooke said.
He flew aircraft dating back to the P-80 Shooting Star, which was later designated F-80 when the Air Force broke away from the Army in the late 1940s. He also piloted the Republic F-84 Thunderjet, the F-86 Sabre and the F-100 Super Sabre, what Cooke called the original supersonic jet.
Cooke said Harris also was fortunate enough to be one of a select number of pilots to fly the F-104 Starfighter, which at one point had been called "the missile with a man in it" by some for its speed and "the widow maker" by others for its safety records.
Cooke said it's "relatively easy" to get a decommissioned fighter plane, but the planes can't have any of the guns or missiles for obvious reasons. Before the Gnat, Harris owned a Fouga Magister, a French trainer and attack fighter. He sold that plane to a museum, Cooke said.
Harris only had the Gnat for three or four years, Cooke said. The plane was designed as a subsonic aircraft but had supersonic capabilities, he said.
"It was kind of hard to fly," Cooke said. "It was the RAF's (Royal Air Force) belief that if they make it hard to fly in training that the pilots would have an easier time when they actually had to fly it in combat."
Only a handful of those planes are in the U.S., he said. The Red Arrows, the United Kingdom's Royal Air Force Aerobatic Team, which is equivalent to the U.S. Navy's Blue Angels and Air Force's Thunderbirds, flew Gnats in their early days. Harris' plane was painted with the same markings as the Red Arrows.
Every plane is different, he said, Harris frequently spoke to pilots, mechanics and engineers in the United Kingdom about his plane. That was how he maintained it, Cooke said.
"John was a mechanic, a pilot and an engineer," Cooke said. "He worked on his own plane."
Harris wasn't a risk taker and didn't take chances with his planes. Cooke said he was "meticulous" in his work because he knew a mistake could be fatal.
Cooke said he and others at the Charleston hangars were shocked. Harris was the "last person you would have thought to go down," he said.
Cooke went up to the hangars Tuesday to see if anyone had heard anything more about the crash. They hadn't, but were speculating.
He guessed it was a mechanical problem or the weather. The 79-year-old pilot was in "excellent" health and appeared younger than his age.
"He was an excellent pilot," Cooke said. "A world-class pilot."
Writer Ashley B. Craig contributed to this report.
Contact writer Charlotte Ferrell Smith at charlo...@dailymail.com or 304-348-1246.