Coronavirus restrictions have thrown the sharing of international crews and aircraft that proved vital during the summer bushfire crisis into doubt and disrupted some hazard reduction activities.

Australasian Fire and Emergency Service Authorities Council chief executive Stuart Ellis said travel restrictions and social distancing requirements to curb the spread of the virus had complicated plans to send fire crews to the US.

Coronavirus restrictions are challenging preparations for next summer's bushfire season. Credit:Nick Moir

Australia, New Zealand, the US and Canada exchange hundreds of firefighters and operational workers as well as an international fleet of 150 public and privately owned water-bombing and spotter planes in their alternate summer seasons.

"Australia drew on 1000 overseas firefighters last summer … that number hasn't been as high previously," Mr Ellis said, adding the "prospect of Australia deploying the same resources to the US which we did in 2017 and 2018, I think that is pretty questionable right now".