OTTAWA—The Liberal government is demanding that the air force have more fighter jets on standby to defend North American and respond to NATO missions, a policy shift that means Canada will need more frontline fighters than first planned.

The change threatens to push the cost of replacing the aging fleet of existing fighters even higher, with the potential of having to spend billions of dollars more to buy more jets than expected.

Lt.-Gen. Michael Hood, the head of the Royal Canadian Air Force, confirmed the shift Monday during an appearance before the Senate defence committee.

“The government has announced a policy whereby the Royal Canadian Air Force is required to simultaneously meet both our NORAD and NATO commitments,” Hood told senators.

“I am at present unable to do that with the present CF-18 fleet. There aren’t enough aircraft to deliver those commitments simultaneously,” he said.

Before the change, while the air force had standing commitments to NORAD and NATO, Hood suggested there was more flexibility to manage the fleet.

“That commitment is now a firm commitment with respect to this policy change so we will meet it,” he said.

“I’ve been told I will be given all the resources I need to increase the numbers available. I’m happy the government is investing in the Royal Canadian Air Force,” he said.

Indeed, Defence Minister Harjit Sajjan said last week the government was not content to “risk manage” its international commitments.

Sajjan made the comments as the federal Liberals revealed plans to move ahead with a lengthy competition for a new fighter to replace the CF-18s now flying. Cabinet ministers also announced plans to explore the purchase of 18 Super Hornet jets as a stopgap measure to help boost the fleet until the new aircraft enter the fleet.

But Hood made plain on Monday that the government has actually changed its approach to meeting its obligations to military alliances in a way that puts more pressure on the air force.

Yet no one is saying just how many fighters are needed to do the job.

Hood said the current fleet of 76 CF-18s—one was lost in a crash Monday – is not sufficient, once maintenance requirements are factored in. Nor would a fleet of 65 modern jets – the number of Lockheed Martin F-35 fighters that the Conservatives proposed buying – be enough either, he said.

Hood refused to say exactly how many jets the air force would need to meet the new demands, saying that number is classified information. “We’ll make recommendations to the number of aircraft that we need to meet that policy,” he said.

Defence analyst Dave Perry said the revelation helps explain the government’s complaints of a “capability gap,” that the existing fleet of CF-18s are unable to meet Canada’s commitments even though upgrades will keep them flying until 2025.

In fact, it appears the Liberals themselves created the gap with the policy change, requiring the air force to have fighters ready to meet demands to protect North American airspace while also responding to NATO needs abroad.

“This government has decided as a matter of policy, it’s now a firm commitment rather than a flexible one,” said Perry, a senior analyst with the Canadian Global Affairs Institute.

And if Canada now requires more than 65 fighters, Perry wonders about the budget.

“They made clear that 65 won’t cut it, I’d be very interested to know where all the money for this is going to come from,” he said.

“Jets are probably the second or third most expensive capability in the armed forces,” he said.