The Canadian companies that are participating in the F-35 fighter jet program are urging the federal government to bypass a competition and return to its original plan to sole-source the purchase of the U.S.-based Lockheed-Martin aircraft.

"Using a competition to simply delay making a decision is costly, unnecessary and not in the interests of Canadian taxpayers or Canadian industry. That is bad management, bad policy and bad for business," the industry group made up of 35 Canadian firms said in an open letter.

But other voices are rising, arguing that the best way to find the aircraft that suits Canada's needs is to launch a competition that would pit the single-engine F-35 against its rivals, including the twin-engine Boeing SuperHornet.

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The debate is at the heart of the choice facing the Conservative government as its seeks a replacement for its aging fleet of CF-18s. Armed with detailed technological information on four fighter jets, the cabinet will have to decide in the coming weeks whether to launch a competition, or to proceed with the untendered purchase of F-35s.

Duff Sullivan, a retired major-general and former fighter pilot, said in an interview that there are lingering questions about the F-35's ability to fulfill one of the key tasks expected of the fighter jet, namely patrolling the Arctic and participating in the defence of North America.

"You could use a single-engine aircraft to do national and continental missions, but there would be greater risk involved. It is as simple as that," he said. "When you lose an engine in a [twin-engine] CF-18, it's a non-event. … When you lose the engine of a single-engine aircraft, the outcome is certain: You will be ejecting from that aircraft."

Mr. Sullivan, who is not working for any firms involved in the current process, oversaw allied air operations in Afghanistan and worked as a defence adviser in the Privy Council Office before retiring in 2010.

He said the F-35's biggest advantage comes at the high end of the spectrum of military operations, such as a hypothetical mission to conduct a pre-emptive strike in North Korea.

But Mr. Sullivan, who has served in Germany and the former Yugoslavia, said Canada has not traditionally participated in these "most extreme, most unlikely" types of missions.

"A competitive process is absolutely required," he said. "It's vital for the selection and the framing of any new fighter aircraft that we are going to get. Why we are not embracing this competitive process is beyond me."

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The F-35 is still in development, and has faced a number of technological challenges that have boosted its price tag. Still, as the most modern fighter on the market, it promises to offer unrivalled stealth capabilities and state-of-the-art capabilities.

The SuperHornet, by contrast, is already in operation and offers more predictable sustainment costs, government officials and experts said.

The opposition parties in the House are also urging the federal government to conduct a competition, pointing out that the sole-sourced process was ripped apart in 2012 by the Auditor-General. The project is estimated to cost at least $45-billion over the new aircraft's lifespan.

Still, the firms that form the Canadian JSF Industry Group said there is much "inaccurate information and rhetoric" behind the calls for a competition. The group said hundreds of millions of dollars in contracts are at stake if Canada does not proceed with its plans to buy the Lockheed-Martin aircraft.

"The short-term reality is that current Canadian F-35 contracts and jobs will very soon start going to countries that are today buying the aircraft," the group said in its open letter.