Qantas is to cut capacity growth, retire aircraft early and shed managers in response to natural disasters in key destinations and rising fuel costs that Australia's national carrier says poses its biggest threat since the global financial crisis.

The measures come on top of two increases in fares on domestic and some international routes since February to help cover rising fuel costs.

Qantas said it would reduce costs and increase revenue by cutting domestic capacity growth in the second half of 2011 to 8% from 14% and cutting international capacity growth to 7% from 10%.

Qantas and its budget stablemate Jetstar will suspend services from Australia to Japan from April to August, and downsize the planes Qantas flies on remaining flights to Japan from Boeing 747s to Airbus 330s.

Jetstar will reduce flights to the earthquake-hit city of Christchurch from other New Zealand cities and from Australia.

The company will also send two B767 planes into early retirement, and reduce management-level staff and leave costs.