A man has died and another has been critically injured in a hang-gliding accident at Lennox Head on the NSW north coast.

Key points: The deceased instructor, from Byron Bay, was described as experienced

The deceased instructor, from Byron Bay, was described as experienced A second man was taken to hospital with head and chest injuries

A second man was taken to hospital with head and chest injuries Witnesses to the event are encouraged to come forward

The dead man is believed to be an experienced local instructor, aged 67, while his passenger — a 26-year-old Irish national — was airlifted to Gold Coast Hospital.

Both men were unconscious when paramedics arrived at the scene at the Pat Morton Lookout just after midday.

Authorities have praised the efforts of up to eight bystanders who did CPR on the men before the arrival of emergency service personnel.

"One patient could not be saved despite the best efforts of bystanders and paramedics," said Inspector Greg Powell from the NSW Ambulance Service.

"The second patient was transported to Gold Coast University Hospital in a critical condition with head injuries and chest injuries.

"It was a difficult scene. There was an embankment of around 4 metres that emergency services had to scramble down and climb back up on numerous occasions," he said.

"The efforts of bystanders and witnesses goes to show how important first aid training, and in particular CPR training, is in moments when you need to wait for emergency services.

"They commenced CPR, they stopped haemorrhage and comforted the patients prior to the arrival of emergency services.

"Some were actually friends of the two victims of the accident so they put their own emotions aside to help their injured friends."

Brett Copeland from the Sports Aviation Federation of Australia described the instructor, a Byron Bay man, as "very experienced".

"He had been flying hang gliders, as far as I'm aware, for close on 30 or more years, and is well regarded by a lot of people in the community and an ambassador for our sport."

"Obviously we extend our greatest condolences to the family," he said.

Police said it's too early to say what caused the crash but local detectives would be leading the investigation.

"Obviously the hang glider will be inspected for any possible faults, witnesses have been identified and will be assisting with this investigation as well," said Inspector David Vandergriend.