Canada's plan to shop for used Australian fighter jets rather than buy new Boeing Super Hornets may backfire, according to defence experts, because the U.S. government will ultimately have a say on whether a deal proceeds.

Even though the FA-18 Hornets are nearly three decades old, require regular corrosion maintenance and are nearing obsolescence, their proposed resale would still require Washington's approval because they are advanced warplanes, originally manufactured in the U.S., a former Royal Australian Air Force officer told CBC News.

"I imagine all of it is going for a fair bargain price," said Peter Layton, a fellow at Griffith University in South East Queensland, Australia, who was a reserve force group captain.

Few customers exist for Australia's used warplanes, and selling to Canada would be an easier sale than most, because the Pentagon would not require all sensitive technology to be stripped out of the aircraft.

But in the context of Canada's current tit-for-tat aerospace trade dispute with the U.S., another defence expert said no one should expect the Trump administration to do Canada any favours in light of the heated rhetoric surrounding Boeing.

"There's a lot of things they could do just within the executive authority to simply be unhelpful," said Dave Perry, an analyst at the Canadian Global Affairs Institute. "I don't know how far they can go, but if the government of the United States didn't want the aircraft to be sold, it would be very difficult to get them."

Corrosion complaints

Australia's defence materiel group produced a scathing report in 2012 noting that the country's FA-18s were rapidly running out of airframe life and required bigger and bigger slices of the maintenance budget.

"The incidence of discovery of airframe corrosion in the Hornet fleet is increasing, and the annual cost of corrosion‐related repairs has increased significantly," said the report, which Layton said was considered "too critical" by the defence establishment.

The Trudeau government has been using the threat of buying used FA-18s from Australia as a bargaining chip in its wider trade dispute with Washington.

On the eve of Prime Minister Justin Trudeau's meeting with U.S. President Donald Trump last week, Public Services and Procurement revealed the Liberal government had sent a letter to Australia expressing interest in buying some of its old fighters.

The department had been talking with Chicago-based Boeing about buying 18 new Super Hornets, but those negotiations were suspended after the giant U.S. aircraft-maker filed a trade complaint against Bombardier over passenger jet sales.

The U.S. Commerce Department intends to impose nearly 300 per cent tariff and anti-dumping duties on the Montreal-based manufacturer's CSeries jet.

Trudeau said Canada no longer has an intention of doing business with Boeing.

Limited to uncontested airspace

The used Australian jets are approximately the same age and configuration as Canada's CF-18s, which the Liberals insist must be supplemented if the air force is to meet its Norad and NATO commitments at the same time.

How well those Australian jets would solve that problem is an open question.

Layton said Canada would likely get only five to seven years' service out of each warplane.

Advances in both fighter jet development and anti-aircraft defences among potential enemies and adversaries mean that Canada's air force, in a just a few years, would be limited to low-intensity conflicts in uncontested skies.

"I think beyond 2020, under most circumstances, you would be very cautious about deploying the aircraft into airspace where it would be likely to meet an opponent that has modern fighter aircraft," said Layton, who has written extensively about air combat issues.

"And by 2025, operating in contested airspace will be very dangerous with the classic Hornet fleet as it is now."

Canada's Liberal government said its moves are intended only as a stopgap until it can replace the entire fleet of CF-18s.

Full competition?

Last spring, Defence Minister Harjit Sajjan promised that open competition would be launched in the immediate aftermath of the new defence policy review, which was released in June.

Public Services and Procurement would only say "preparatory work" for that tender is still underway.

Perry, the defence analyst, said no one has been able to convincingly explain why it is on the back burner.

"I don't understand why moving ahead with the competition isn't the best overall solution," he said. "You would avoid any of the difficulties of introducing an interim fleet."

Perry has long been a critic of the notion of a stopgap fleet, but recently noted that buying used was better than buying new Super Hornets.

Although the Australian FA-18s are almost identical to the CF-18s, there are some differences, notably in software, air-to-surface weapons and the life-extension work that has been carried out on them.

Only 10 fighters in the Australian fleet have received the kind of extensive airframe reinforcement that Canada paid for in its jets.

"I could conceive of your air force using them as an expensive training aircraft," said Layton.