OTTAWA -- The federal Liberal government says it will "explore the acquisition" of 18 new Boeing-made Super Hornet jets on an interim basis until it can decide on a permanent replacement for Canada's aging fleet of fighter planes.

The government plans to meet with the U.S. and Boeing to purchase the 18 planes "at a cost, time, level of capability and economic value that is acceptable to Canada" in order to fill a "capability gap" in the country's air defences.

The decision marks what will surely be another controversial turning point in the long, protracted effort to replace the air force's workhorse CF-18s, which Defence Minister Harjit Sajjan says are long past due for replacement.

"The government will launch, in its current mandate, a wide-open and transparent competition to replace the CF-18 fleet," Sajjan told a news conference Tuesday.

In addition, we will enter into discussions immediately with Boeing on the acquisition of 18 Super Hornets to address the capability gap."

Sajjan said the military will implement a range of new measures including recruitment and training in order to extend the range of service of the existing CF-18 fleet.

"All of these actions, taken together, are necessary to address the situation this government has inherited."

This past spring, the government had been eyeing the Super Hornets as a stop-gap option until an outcry from industry and the opposition forced them back to the drawing board.

During last year's election campaign, Prime Minister Justin Trudeau promised not to purchase Lockheed Martin's F-35 stealth fighter, long the preferred option of the previous Conservative government.

The government has been struggling with how to fulfil that promise for fear any attempt to exclude the stealth fighter from a competition would result in a multibillion-dollar lawsuit.

Canada will remain a member of the multinational Joint Strike Fighter program, which gave rise to the F-35, Sajjan added.

"With this investment in the Royal Canadian Air Force over the short and long term, Canadian air space will be better defended," said Gen. Jonathan Vance, Canada's chief of the defence staff.

"We will be a stronger partner in our own defence through Norad and we will have the capacity to meet our NATO obligations and continue to contribute meaningfully to global security."

There is precedent for buying Super Hornets on an interim basis after Australia bought 24 of the aircraft to replace antiquated F-111 jets until newer F-35s were ready.

However, the idea of Canada needing to follow suit was largely dismissed by a government-appointed expert panel and the military's research branch as too expensive, since the air force would be operating two types of aircraft, demanding different training, infrastructure and supporting equipment.

One key question will be how much the Super Hornets would cost.

The Liberals pegged the cost of one F-35 at $175 million and one Super Hornet at $65 million, but those numbers have been repeatedly questioned.

Meanwhile, Kuwait recently announced plans to buy 40 Super Hornets for $13 billion. While the deal includes eight Super Hornets dedicated to electronic warfare, that still works out to $335 million per plane.

At the same time, Denmark is moving ahead with plans to buy 27 F-35s at a cost of $4 billion, which amounts to about $148 million per plane.

Even then, both Boeing and Lockheed Martin have said comparisons with other countries do not reveal the true costs for Canada, which would require a different package than other countries.

There is also the issue of how much Canadian business would benefit from the decision.

The Liberal government paid $33 million in June to stay within the F-35 program, bringing Canada's total contribution to $311 million since 1997.

The government's argument for making the payment was to keep Canadian companies in the running for billions of dollars in work, of which they have so far received more than $1 billion.

Industry Canada estimated in December 2014 that Canadian companies could win more than $9.5 billion in work associated with the F-35.

Supporters of the F-35 have said such contracts would represent leading-edge work for Canada's aerospace sector and see them feeding into a global supply chain in support of the stealth fighter.

But the work is also not guaranteed, and Canadian companies would need to compete for each contract.

In contrast, Boeing would likely be bound by the government's long-standing rule that requires foreign companies to re-invest into Canada after winning federal contracts.

The policy has been previously criticized, while critics say any work associated with the Super Hornet would be on old technology.

But Boeing indicated in the summer that it could target those required investments by expanding its sizable commercial operations in Canada.