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 says it plans to discuss the issue with the U.S. and Boeing to determine whether Super Hornets can be procured "at a cost, time, level of capability and economic value that is acceptable to Canada."

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.

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.

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, 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.