Corporal David Morris watched in horror as Flight Lieutenant Sean Cunningham, 35, was propelled 200 to 300ft in the air from his Hawk T1 aircraft while on the ground at RAF Scampton, Lincolnshire, on November 8 2011.
He was a highly-regarded and experienced pilot with the RAF's aerial display team as well as an Iraq war veteran, but was fatally injured after being ejected.
The parachute on the ejector seat did not deploy and he died in hospital as a result of multiple injuries.
Giving evidence to the inquest in Lincoln, Cpl Morris, a Survival Equipment Fitter or "squipper" with the RAF, said he was not far from the jet at the time.
"The canopy filled with smoke and Flight Lieutenant Cunningham went from his seat through the canopy," he said.
Cpl Morris was forced to pause to compose himself before he continued talking.
"He came down almost in slow motion, but obviously fairly quickly, and hit the floor. I could hear and feel the thud beneath our feet."
Colleagues rushed to Flt Lt Cunningham's side but Cpl Morris said it was obvious he was terribly injured.
"I knew it was bad," he told the inquest.
Asked by Richard Seabrook, counsel to the inquest, if he saw any signs of life, Cpl Morris paused to take a deep breath before answering: "No."
The inquest, which is expected to last up to three weeks, continues.