One of the Canadian air force spy planes assigned to the campaign against ISIS has been quietly withdrawn and brought home, CBC News has learned.

The CP-140 Aurora, with a suite of high-tech surveillance equipment, was one of two that had been flying missions over northern Iraq and Syria since the fall of 2014.

The decision to bring one of the turboprop aircraft home was not announced by the Liberal government, which recently extended the deployment of the Canadian military, including special forces trainers on the ground, until the end of June.

A single CP-140 and a refuelling tanker remain in Kuwait, where the Canadian Air Task Force has been based, to continue operations alongside the U.S.-led coalition.

But the decision could signal the beginning of the end of Canada's military involvement in the anti-ISIS fight.

A spokesperson for the military's operations command said the Aurora was withdrawn on May 15 and its departure has not impeded the coalition's air campaign against the militants fighting to establish an Islamist state.

"The [Canadian Armed Forces] shared its intent to return the aircraft to Canada with our coalition partners well in advance in order to ensure continuity in the coalition's intelligence, surveillance and reconnaissance operations against Daesh," said Capt. Vincent Bouchard, referring to ISIS by its Arabic acronym.

Battle for Mosul

Iraqi security forces and Kurdish fighters are close to liberating the northern Iraqi city of Mosul and when the bloody campaign is completed, ISIS will largely have been driven from the country.

In an email on Tuesday, Bouchard painted the decision to remove one of the CP-140s as a routine matter, meant "to effectively balance its expeditionary requirements and domestic commitments." He said the aircraft was needed to "deliver on its full range of missions domestically."

The primary mission of the CP-140s in Iraq was to act as spotters, targeting ISIS combat units and buildings for destruction.

In February 2016, Defence Minister Harjit Sajjan told the House of Commons that Canada's CF-18 fighter jets had completed their bombing mission in Iraq and Syria. At that time, the Liberal government took pains to underline it was leaving the spy planes and tanker in place. (Sean Kilpatrick/Canadian Press)

When Canada's CF-18 fighter jets were withdrawn from the bombing campaign in February 2016, the Liberal government took pains to underline it was leaving the spy planes and tanker in place to support other coalition members as they continued combat operations.

As of May 20, the Auroras had flown 793 reconnaissance missions.

Special forces in northern Iraq

Canada still has more than 200 special forces troops advising Kurdish and Iraqi forces, as well as a tactical helicopter detachment, a number of intelligence officers and a Role 2 combat hospital deployed in Iraq.

The mission was reviewed in March, but only given a three-month mandate extension, to June 30.

Kurdish Peshmerga commanders have asked that highly trained special forces remain behind once Mosul is freed in order to help with training in counter-insurgency warfare.

Many experts and U.S. commanders have said expelling ISIS from Iraq will not entirely end the fighting and that extremists will likely resort to hit-and-run guerilla tactics.

The Liberal government has been unclear on whether it's prepared to facilitate that kind of training or participate in reconstruction efforts.

Beginning of the end?

Prime Minister Justin Trudeau, speaking at the NATO Summit on Thursday, would not say what lies ahead for Canadian involvement in Iraq and attempted to paint the aircraft's return as a routine matter.

"This was simply part of a regular rotation that was foreseen, that other countries were going to step in," he said in Brussels. "There is nothing surprising or sudden about this. This was always part of the plan."

The removal of the Aurora is a signal to defence analysts that the deployment could be coming to an end.

"If this is not the end of the mission, it seems a bit strange they would be pulling out one of these aircraft, which arguably has been one of the most important parts of our contribution," said Richard Cohen, who was an adviser to former defence minister Peter MacKay and served in both the Canadian and British militaries.

Given the deployment of troops to Latvia next month and the Liberal government's plan to return to peacekeeping, he said the military might not have the bodies to sustain an extended commitment in Iraq.

Four Canadian aircrew who fly one of the country's CP-140 surveillance planes leave the flight line at an unidentified coalition airbase in Kuwait on Nov. 13, 2016. (Murray Brewster/CBC)

The question of what Canada is going to do post-Mosul has been met with resounding silence, said Steve Saideman, a professor of international affairs at Carleton University in Ottawa.

The U.S.-led coalition has been organizing the next phase of the anti-ISIS campaign, with a finite number of positions, and Canada has yet to apparently signal interest.

"Canada has no role there," Saideman said. "And what that's going to lead to is dumb politics, shockingly enough."

By not articulating a clear way forward in the fight against ISIS, the Liberals have opened themselves up to criticism from Opposition Conservatives and possibly allies, he said.

The future of the Iraq mission could be made clear with the release of Canada's long-awaited defence policy on June 7, but Saideman said it's unlikely to change the narrative.

"The fact is Canada may not be needed, and given the tempo of special forces operations, it might be time for them to come home and relax," he said. "But that's not going to be the conversation. The conservation is going to be about [how] Canada doesn't care about Iraq."

Dealing with terrorism, and specifically ISIS, is a top priority for the Trump administration. The U.S. leader recently scored a victory on that front, as NATO commanders moved to endorse a plan to formally join the U.S.-led coalition in Iraq and Syria.