The head of the Royal Canadian Air Force says all 77 of Canada's CF-18 fighter jets will be able to fly until 2025, and even later.

Lt.-Gen. Michael Hood also says the U.S. military and other allies are working on upgrades to the aging aircraft that would reduce the risks and costs if they are needed for even longer periods of time.

The comments are contained in documents filed this week with the House of Commons defence committee as the Liberal government prepares to negotiate the purchase of 18 new Super Hornet fighter jets.

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The government says it needs the Hornets to address an urgent shortage of warplanes until a competition to replace all 77 of Canada's CF-18s can be finished – a process it says could take up to five years.

Defence Minister Harjit Sajjan's office says Hood's comments don't address the "capability gap" that has been created from many CF-18s being out of service on any given day because of maintenance issues.

"Keeping old planes flying longer won't address the capability gap," spokeswoman Jordan Owens said in an email.

"With the current availability rate what it is, even if the 77 airplanes could fly forever, there still wouldn't be enough of them to simultaneously meet our NORAD and NATO commitments."

The government and National Defence have refused to say how many jets Canada actually needs at any given time, saying that to reveal the numbers would jeopardize national security.

But others say the general's comments are a clear indication he is comfortable with the state of Canada's CF-18 fleet, and that buying the Hornets before a competition is unnecessary and politically motivated.

"Anyone reading (Hood's) comments would come to the conclusion that there is no capability gap," said Alan Williams, a former head of military procurement at National Defence.

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Critics have suggested the Liberal decision to buy Hornets now and punt the competition down the road is part of a larger Liberal plan to avoid buying the F-35 stealth fighter.

The defence committee had asked Hood to clarify comments he made in April, when he said the air force would be in a "comfortable position" as long as a replacement for the CF-18s was selected in five years.

In the written response received by the committee on Monday, Hood said he was "confident that, based on the latest information available, there is sufficient capability to support a transition to a replacement fighter capability based on the ongoing projects and planned life extension to 2025 for the CF-18."

He added that new upgrades being developed and implemented by allies "would reduce operational, technical and cost risks to Canada's CF-18 fleet if additional capability improvements are required."

Another section of the response says "all 77 CF-18 aircraft can be flown to 2025 should there be a need to do so, and retiring the fleet beyond 2025 is feasible with additional investments and continued management."

Defence analyst David Perry of the Canadian Global Affairs Institute said his reading was the same as Williams: that Hood believed he could keep enough CF-18s in the air until a replacement was picked.

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"However you want to parse the words, he's talking about the ability to meet Canadian defence policy," Perry said.

"Based on previous defence policy direction, Gen. Hood was confident that he could meet that so long as a decision was taken within another five years."

Conservative defence critic James Bezan said Hood's comments confirm what the opposition and others have said since the spring, when the Liberals' first planned to buy Hornets: there is no "capability gap."

"This is the greatest hoax going, that there's a capability gap," Bezan said. "And it speaks to the Liberals trying to frame a sole-source decision under false pretences."

Hood will get a chance to clarify his remarks when he testifies before the Senate defence committee on Monday. It will be his first public appearance since the Liberals announced their plan to buy Hornets.