Delays create a sting in the tail for ageing Hornets

The Australian National Audit Office said there was a limit to how much the Australian Defence Force could extend the F/A-18 Hornet's life to cover even greater JSF delays. That would be costly and could result in reduced capability, it said.

Later this year, the ADF will present options on managing the transition, including a limited extension of the planned 2020 withdrawal date of the older Hornets, which entered service in the mid-1980s.

Buying more Super Hornets, beyond the 24 now in service, is also likely to be considered, to ensure there is no capability gap between the retirement of older Hornets and the introduction of the JSF.

The audit office said the F/A-18's operational life was likely to be extended.

But it would be a challenge to co-ordinate the highly complex and costly procurement and introduction to service of JSF, with sustaining older aircraft to ensure there was no capability gap, it said.

Australia is looking to buy up to 100 of the Lockheed Martin F-35 Lightning JSFs as the RAAF's principal combat aircraft in a deal worth about $US13 billion ($A12.5 billion).

So far it has firmly committed to take delivery of just two, which are scheduled for arrival in 2014.

The audit office said JSF development had proceeded more slowly and at greater cost than first estimated, and its advanced technology gave even the US Defence Department difficulties in assessing the time and cost of developing and operating the aircraft.

"Although current estimates of the F-35's performance are close to those required, performance will not be fully demonstrated until the completion of initial operational tests and evaluation, presently expected in February 2019," it said.

The cost of a JSF is expected to drop from $127 million to $80 million as the production rate increases.