OTTAWA -- The Trudeau government is adding a new requirement to how it picks the winners of major military contracts by assessing a company's overall impact on the Canadian economy.

The government is also launching a full competition to replace Canada's aging CF-18s with 88 new fighters, a move that comes in the midst of an ongoing trade dispute with U.S. aerospace giant Boeing.

"After extensive consultations and careful analysis as part of the defence policy review, it was clear that a full fleet of 88 planes are required to fully meet our Norad and NATO obligations simultaneously," Defence Minister Harjiit Sajjan told a news conference.

"Our government will not risk-manage our national defence commitments."

Boeing has been eager to submit its Super Hornet to compete for the contract, which is valued at up to $19 billion and expected to start delivering jets in 2025.

But the government's change to how competitions are run could have an impact on Boeing if its trade dispute with Canadian rival Bombardier is still alive and ends up being deemed harmful to Canada's economic interests.

"Getting a new fleet of aircraft represents a once in a generation opportunity for Canada's aerospace and defence industries," said Procurement Minister Carla Qualtrough.

The Liberals are also officially abandoning a plan to buy 18 Super Hornets to temporarily boost Canada's CF-18 fleet, saying they plan instead to buy 18 second-hand fighter jets from Australia.

"We have received an offer for sale of F-18 aircraft from the government of Australia, which we intend to pursue, and we have received an offer of Super Hornets from the U.S. government, which we intend to let expire," Qualtrough said.

Officials briefing reporters on background say that while details are still being worked out, the used Australian jets will cost significantly less than Super Hornets and can be put into action two years faster.

Since Canada already flies a version of the same fighter jet, "the supply chain and maintenance lines required to support these aircraft are already in place," Sajjan said.