Richie McCaw flying against the fire

Former All Blacks captain Richie McCaw says seeing the devastation caused by the Christchurch Port Hills fire has been a reality check.

"Jeepers, when you see flames burning so close to the city it's scary stuff," he told The AM Show.

McCaw has been flying missions since the fires broke out on Monday. McCaw, who began working at Christchurch Helicopters after he retired from the All Blacks in 2015, says it's a rewarding job.

"I'm hugely passionate about flying. I think the big thing that I've enjoyed especially around the earthquakes, and now this, is you're actually flying to help people."

He says the death of helicopter pilot Steve Askin, who crashed while fighting the fires on Tuesday, was a huge shock which most people still haven't had time to process