One of the final messages from the three American firefighters who died on a water-bombing aircraft while fighting the Australian bushfires has been revealed.

An interim report released by the Australian Transport Safety Bureau revealed the final moments before the aircraft crashed, which killed all on board instantly.

First Officer Paul Hudson, flight engineer Rick DeMorgan Jr and Captain Ian McBeth died on January 23rd after completing a waterbombing mission on an out-of-control bushfire near the Snowy Mountains.

“Don’t send anybody and we’re not going back,” their final message said.

After the crew completed the retardant drop, they sent a text message to a spotter pilot saying that conditions were "horrible down there".

“They also reported to the Cooma Fire Control Command that the conditions were unsuitable for firebombing operations,” the report read, according to APN.

The report revealed there was “no appreciable change in the centre of gravity following a retardant drop” and that the voice recorder in the plane was not working.

There was no distress call before the crash and as the plane began to descend, it hit the ground at around 280km/h and created another bushfire.

The trio worked for the US charter company Coulson Aviation which had been contracted by the NSW Rural Fire Service to fight the bushfires.

NSW RFS Commissioner Shane Fitzsimmons said the men were dedicated to the "art" of aerial firefighting.

"It's a body blow for everyone in the firefighting fraternity, in the community of NSW and further afield," he told reporters in Sydney at the time.

"It's a confronting and sobering reminder of the enormity of the risk and challenge associated with this fire season."

Photo credits: Coulson Aviation