Passengers have described the moment their flight from Melbourne to Canberra entered a fire-generated weather system over south-eastern Australia.

Key points: Qantas flight hits unexpected turbulence inside fire-generated weather system

Qantas flight hits unexpected turbulence inside fire-generated weather system Passengers recall panic as outside "went pitch black"

Passengers recall panic as outside "went pitch black" The plane was greeted by emergency services, but no injuries were reported

The Qantas flight's route took it over bushfires ravaging Victoria and New South Wales and the plane unexpectedly entered a weather system being generated by one of the fires.

"It just got greyer and greyer," passenger Matt McIntyre said of the approach to the pyrocumulus cloud.

"All of a sudden just pitch black, and that's when the plane sort of dropped.

"There was one guy sort of swearing … I heard people down the front vomiting."

Another passenger said it was "the scariest flight" she had taken.

These images were taken minutes apart as the plane flew into the cloud. ( Supplied: Matt McIntyre )

"It was orange outside of the window, then suddenly it was black, and then the turbulence hit," she said.

"I was jumping off my seat!"

Pyrocumulous clouds emerge when hot air from fires rises into the sky and cools, causing condensation and the formation of clouds.

Qantas fleet safety captain Debbie Slade said pilots reacted quickly to hitting the unexpected turbulence.

"The pilots ascended to a higher altitude before taking a different approach into Canberra, where the aircraft had a normal landing," she said.

Pyrocumulous clouds have been forming over south-eastern Australia. ( Facebook: Jodie Wilkinson )

Mr McIntyre said the plane's passage through the cloud felt as though it went on for minutes, but was likely shorter than that.

"Because it was so dark outside, it was just hard to get a gauge on exactly what was happening," he said.

"It wasn't until we got back on track that we got a voiceover from the captain.

"They said it just did not come up on the radar at all.

"One minute we were in daylight, the next, it was midnight."

The plane was met on the ground by emergency services, but no injuries were sustained by passengers.

Mr McIntyre said once the plane had landed safely, the captain greeted passengers and ensured they were OK.

"It's the first time I've been on a plane where you land and the captain gets a round of applause, that's for sure," he said.