A plan to buy 18 Boeing Super Hornet fighter jets is expected to be scrapped amid Canada's deepening fight with the aerospace company, and the country could announce this week it intends to acquire a used fleet of older Australian F/A-18A/B Hornets.

Australia's Defence Department confirmed Canada had shown interest in buying the jets, which would extend the life of its fleet of F-18s as it pursues a longer-term plan to replace ageing aircraft.

Australian military experts said the planes would meet Canada's defence needs, which are relieved partly by the US' capabilities, but are likely to require maintenance for structural wear and fatigue.

Visiting fellow at Griffith Asia Institute, Griffith University Peter Layton said Canada would pay a low price for the aircraft, which would be cheaper to fly than the Super Hornets it initially planned to buy.

However the money paid would only maintain a "second-string" fleet of aircraft, and its military would need to monitor the planes closely, Dr Layton said.

Australia is buying 72 F-35 Joint Strike Fighters from the US to replace its Hornets and the Defence department is following a plan to dispose of its 71 ageing F-18s, which form the backbone of the air force's combat and airborne ground-attack capability.

The Hornets entered service between 1985-1990, and were originally to be withdrawn from service in the five years to 2015 before the federal government extended the withdrawal period.

A national auditor-general report found in 2012 that as the planes aged there were risks of more airframe corrosion and fatigue issues making maintenance more difficult and expensive.

"Extending the F/A 18A/B fleet's planned withdrawal date beyond 2020 may well require the fleet to undergo an expanded, and hence more costly, safety-by-inspection regime, structural modifications program and capability upgrades," it said.

Director of the Australian Strategic Policy Institute's defence and strategy program Andrew Davies said the US Marine Corps was planning to extend the life of its own F-18s by many years.

Buying Australia's Hornets would be an interim measure for Canada, Dr Davies said.

"They are always going to be old aeroplanes with capability that goes back to the mid-2000s," he said.

A surge in flying hours for the Hornets in recent years indicated that, despite their age, Australia's maintenance of the fleet had kept it in good condition for Canada.

"Provided they don't pay too much for them, it should give them a chance to keep their fleet going into the 2020s until they decide what to do in the longer-term," Dr Davies said.

"It's actually not a bad deal for Australia either, as there is often a cost to disposing military equipment."

A 2010 assessment of the aircraft showed they were structurally in better shape than expected, he said.

The Defence department said it received an expression of interest from Canada in September to buy the planes.

"Defence is continuing to assist Canada in regards to their EOI," a spokesman said.

Canada's dispute with Boeing centres on a decision by the company to launch a trade challenge against Canadian planemaker Bombardier Inc over accusations it had dumped airliners on the US market.