Federal officials tried to cut through the fog of war last year when they told Finance Minister Bill Morneau that it would probably be cheaper to replace Canada's aging Air Force fleet with Super Hornet fighter jets rather than F-35s.

The cost of each warplane has been a matter of sharp debate for years as successive Canadian governments have wrestled with the politically thorny question of how best to usher the force into the 21st century.

That uncertainty was evident in a secret briefing note presented to Morneau in August and obtained by The Canadian Press through the Access to Information Act.

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But using publicly available information, officials were able to provide "rough estimates" of the cost of each of the different aircraft in the running to replace the CF-18s.

The Super Hornet came out best: officials pegged the average cost of each jet at between $88-million and $110-million, depending on the source of information and which of the various options were included.

That compared with between $110-million and $144-million for an F-35, while two European fighters also in the running were even more expensive.

Officials cautioned that the actual price to Canada would depend on a number of factors, such as the exchange rate, what Canadian-specific modifications were included and, ultimately, the number of aircraft purchased.

They also said they were unable to determine the full cost not only of buying, but also operating and maintaining each type of jet – details that some analysts consider to be even more important than the sticker price.

But the figures do provide insight into the information that has been presented to decision-makers in Ottawa when it comes to one of the most politically sensitive and contentious military projects in recent political history.

A few months after the note was presented to Morneau, the Liberal government announced plans to sole-source 18 Super Hornets as a stop-gap measure before running a full competition to replace the CF-18s.

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The government says the Super Hornets are urgently needed because of a shortage of airworthy CF-18s, but opposition critics and others allege the plan is actually part of a larger effort to avoid buying the F-35.

The figures contained in the briefing note suggest buying those 18 Super Hornets would cost between $1.5-billion and $2-billion, though manufacturer Boeing has until the fall to provide a final cost.

The government has not said when it plans to launch the actual competition to replace the full CF-18 fleet.

Defence Minister Harjit Sajjan has said the Liberals want more than 65 new planes, which is how many F-35s the previous Conservative government had planned to buy for $9-billion before putting the project on indefinite hold.

While F-35 manufacturer Lockheed Martin did not want to comment on the briefing note Thursday, spokeswoman Cindy Tessier defended the stealth fighter as the best jet for Canada.

"Lockheed Martin is confident that the F-35 represents the right solution for Canada at the most affordable cost, delivering the most capable fighter aircraft and resulting in the greatest economic opportunity to Canadian industry," Tessier said in an email.

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The briefing note nonetheless represents another blow to the company's continuing and seemingly uphill battle to sell the controversial fighter to the Liberals.

Prime Minister Justin Trudeau told the House of Commons last year that the F-35 "does not work and is far from working," and promised during the 2015 election campaign not to buy it.

The Liberals have since backed off that promise, saying the F-35 is free to run in a competition, though government officials have continued to raise questions about the aircraft.

The government's decision to purchase Super Hornets, even on an interim basis, has nonetheless been widely panned by opposition critics, defence experts and retired military officers.

Thirteen senior officers wrote to Trudeau in February asking him to reconsider his plan, saying the measure would hurt the military in the long run.