As the first ever deployment of American firefighters made the descent into Sydney from the United States on Saturday morning, the bushfire smoke cloaking the city for the past week filled the aircraft cabin. For firefighting aviation specialist Michelle Moore, from Idaho, the smell wasn’t alarming.

"I understand it’s pretty traumatic for you guys, but it’s something we deal with - it’s our comfort zone," she said. "It smells like it’s time to go to work."

Aviation specialist Michelle Moore. Credit:Edwina Pickles

Ms Moore is one of 21 specialist firefighting personnel from the US, and another 21 from Canada, to join NSW’s "marathon" effort to contain bushfires that now stretch along the entire coast and have, since July, burnt through two million hectares and destroyed more than 680 homes.

While NSW has sent firefighters to the US every year for the past two decades, it’s the first time the Rural Fire Service has made the call for a full-scale reciprocal response.