When pilot Nathan Koch makes his way to the flight deck at Canberra airport, he sometimes takes a few passengers with him and stows them in the cockpit.

Mr Koch, who is also a practising vet, is helping to save the critically endangered southern brush-tailed rock wallaby from extinction by taking joeys along for the ride from Canberra to Adelaide.

He is volunteering his time as part of a breeding program which involves the transfer of wallaby joeys from Canberra's Tidbinbilla Nature Reserve, so they can be fostered by mothers of a more common, similar species at Adelaide Zoo.

The partnership between Canberra's Tidbinbilla Nature Reserve, Adelaide Zoo and Qantas is helping southern brush-tailed rock wallabies breed more quickly and boost their dwindling populations.

Mr Koch said there was only a small window of opportunity to transport the joeys so he sometimes carried them on flights he was piloting and at other times travelled as a passenger while looking out for the precious cargo.

Pilot Nathan Koch holds a humidicrib with wallaby joeys in the cockpit of a domestic flight at Canberra airport. ( Supplied: Brent Winstone )

"The people from Tidbinbilla have them all decked out and ready to go in their high moisture content containers so it's really just making sure their temperature is okay," he said.

"I just keep an eye on them and make sure they haven't got tangled up in their little cloth."

The trip can be out of the way for Mr Koch, who is based in Perth, but he said he was happy to volunteer his time.

"To be able to have an involvement in something as important as protecting a species or helping a species to survive, I really feel very privileged to be able to do that," he said.

Mr Koch said his involvement in the project came about by accident several years ago and he has since transferred eight joeys.

"On one flight I happened to have one of the vets from Adelaide Zoo who had one of the southern brush-tailed rock wallaby joeys with him, so we got talking," he said.

"From there it came about that I started to take the wallabies from Canberra to Adelaide and Qantas has supported me in that."

Rangers dubbed one of the transferred joeys "Kochie" in the pilot's honour.

Tidbinbilla rangers thankful pilot is on board

Nathan Koch receives advice from Scott Ryan and Kym Birgan as he takes charge of the joeys. ( ABC News: Kathleen Dyett )

Scott Ryan from Tidbinbilla Nature Reserve said Mr Koch's help was invaluable.

"We'd need to send a vet if we didn't have Nathan's help so for him to come on board in this partnership and help us out, being a pilot as well as a vet is quite incredible," he said.

"We've just had such a really good year with the breeding of rock wallabies at Tidbinbilla that we're literally running out of pouch space."

Tidbinbilla's acting project officer of the wallaby breeding program, Kym Birgan, said there were a few steps involved in safely packing the joeys for the flight.

"We remove the joey from the mother's pouch, pop the joey in the humidicrib, make sure that it's moist because it needs to be humid and then bring it to the airport for Nathan," she said.

Nathan Koch carries his precious cargo to and from the flight deck. ( ABC News: Kathleen Dyett )

"The program's been hugely successful. Since 2009, 72 southern brush-tailed rock wallabies have birthed at Tidbinbilla so that's very exciting."

Adelaide Zoo's senior keeper of Australian natives, Nathan Langley, said after the joeys arrived in South Australia, they were placed into the pouch of yellow-footed rock wallabies because they are a very similar species.

"The whole reproduction process start to finish is pretty much the same as what a brush-tailed rock wallaby's would be," he said.

The joeys spend about six months in the pouch of their foster mother in Adelaide before their release into an enclosure and eventually the wild, with many of the wallabies returning to the ACT.

But Mr Langley said it was important to keep an eye on the wallabies as they grew up.

"The brush-tailed rock wallabies are unbelievably agile," he said.

"They can jump and climb and carry on. The brushies manage to jump between exhibits that are eight to nine feet tall."

Tidbinbilla Nature Reserve has sent 25 joeys to Adelaide Zoo since 2009.