The Kiwi Commander in charge of New Zealand's evacuation effort in Afghanistan has spoken for the first time about just how difficult the mission was.

Group Captain Nick Olney compared the rescue to pulling people from a mosh pit, and says they were lucky not to have been at the airport when the first suicide bomber struck.

Flying over a city under Taliban control, our Defence Force (NZDF) lands at Kabul's International Airport, taxiing past lines of people boarding aircraft from around the world in a race to evacuate as many as possible.

Olney and his team had less than one hour to load people onboard and take off again.

"It's pretty slick; it's like a Formula 1 operating party there," he said.

Our Defence Force made three successful evacuation flights to Kabul, but it wasn't easy scouring crowds of thousands outside the airport to identify Kiwis and Afghans who helped us during the war.

"It's absolute sheer luck on the ground that some of these people found us - it's a New Zealand baseball cap on a soldier or a Kiwi or a New Zealand flag."

And sheer desperation. A defining image of the chaos at Kabul airport was the sight of Afghans clinging and falling from the side of a US Air Force Plane and the crush of people trying to get into the airport, where NZDF soldiers were waiting to help.

"We were swimming people through sewage ditches and pulling them up through barbed wire fences," said Olney.

"If you're looking for a mental image to paint, reaching into a mosh pit at a concert and trying to bring your mate through and occasionally you let go of hands."

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That was the difference between making it and being left behind. The team on the ground - it's tormenting for them.

That feeling hit again when a suicide attack outside the airport killed more than 100 people - among them, 13 US Marines.

One by one their bodies were returned home on Monday (NZ time) - flags cloaked over coffins that could easily have been ours.

"Some of our troops on the ground likely knew them, we were working alongside those people - that's exactly where our soldiers were," said Olney.

Nearly 300 New Zealanders made it out of Kabul on evacuation flights, but many more didn't.

"The hardest part for me is that we've left people behind," Olney said.

Left behind to face an uncertain future under Taliban control.