A Toronto man was recovering Friday after both his main parachute and a secondary chute failed to open properly during a jump in Hamilton to commemorate D-Day.

The 44-year-old was taking part in a demonstration to mark the 75th anniversary of D-Day at the John C. Munro Hamilton International Airport on Thursday afternoon, police said.

Investigators said "trouble began" when the man's main parachute appeared to become tangled. He deployed a secondary chute but that didn't open effectively either, although police said it did slow his fall.

The man, who police called an experienced skydiver, was taken to hospital with non-life-threatening injuries.

Fred Vermeer, who works at the airport and captured video of the incident, said he felt sick to his stomach watching the skydiver plummet to the ground.

"I thought I'd just watched somebody die," Vermeer said in a phone interview. "It was pretty freaky. He hit the ground pretty hard."

The jump appeared to be going well at first, Vermeer said, but it quickly became apparent that something was wrong.

"As he was going down, he started pirouetting. I thought it was just part of an acrobatic display ... but he didn't stop doing it," Vermeer said, adding that he started filming so that there would be evidence of the incident.

Another witness, Marianne Hobson, had been working from her home office in Hamilton on Thursday when her partner suggested they go to the airport to check out the D-Day event.

Hobson, an amateur photographer and real estate agent, said she had zoomed in on the parachutist as his parachute appeared to malfunction.

"It was enough, thank God, to slow him down enough and break his fall," she said. "Because it would have been tragic if it hadn't opened at all."

Hamilton police said Transport Canada was informed of the incident. The federal agency said it was aware of what happened but noted that parachuting fell outside its mandate.

The Canadian Warplane Heritage Museum, which organized the D-Day event, did not respond to a request for comment on Friday.

In a Facebook post ahead of the event, the museum said skydivers would be jumping from a restored Douglas C-47 Dakota "to commemorate the paratroopers who would have done so 75 years ago."