Canada's problems with its planned purchase of F-35 Lightning Joint Strike Fighter aircraft seem to be multiplying, with the latest controversy surrounding the jets' capacity for in-flight refueling.

With Canada's confirmation of the planned multibillion-dollar purchase still months away, and continuing uncertainty over the numbers Ottawa may eventually buy, questions are being raised about how the F-35 Joint Strike Fighters will refuel when deployed by the Canadian air force.

The outlook for the refueling dilemma remains unclear. Canada will rely on either private companies or its allies for in-flight refueling if it decides to purchase the F-35s to replace CF-18 fighter aircraft, Defense News said on its website.

But if the outsourcing does occur one way or another that will pit Canada against embarrassing issues of national sovereignty, especially if the air force is forced to request refueling assistance from other allied forces.

But critics and analysts say the decision raises key issues about Canadian sovereignty and military capabilities.

A recent independent audit of the government's plans to buy F-35s revealed that current estimates for the planned purchase had no provision for modifying the F-35s so that they could be refueled in flight by Canadian air force jets.

The alternatives being faced by the Canadian military include refueling through a private agency or refueling by a friendly government's aircraft.

In either case, the costs for Canada will be multiple and complex. Not only are Ministry of Defense plans silent on the actual cost of refueling the jet fighters but they also don't consider the diplomatic and political implications of expecting other nations' aircraft to refuel the F-35s after a multibillion-dollar purchase and deployment of the aircraft.

A 30-page audit by KPMG accountancy and tax advisory firm noted the Canadian defense department will have to rely on the North American Aerospace Defense Command, "coalition partners or commercial refueling assets to meet operational requirements."

The audit report, "Next Generation Fighter Capability," was released in December.

The F-35A jets earmarked for purchase by Canada will use a boom refueling system in contrast to the air force's current practice of using CC-150 Polaris tankers, which employ the probe-and-drogue system. That system is used by the F35-B and F35-C but is not compatible with the F-35s planned to be purchased by Ottawa.

Aircraft manufacturer Lockheed Martin says Canada will have the option to choose either or both refueling systems. Critics want to know how that will affect the jet's weight and functionality.

Confusion over the refueling capacity of Canada's premier fighter jets drew criticism from analysts and experts.

Alan Williams, a former head of procurement who was among those who approved Canada's participation in the F-35 program, said the department's plan makes no sense, Defense News reported.

"Are we going to spend a large amount of money on new fighters and then rely on allies to refuel aircraft over Canadian territory?" he asked. "Is Canada no longer a sovereign country?"

Defense analyst Martin Shadwick described the decision as a step backward for the Canadian air force.

The refueling issue is especially sensitive in Canada because of past blunders with the procurement program. Canadian forces had to do without strategic air-to-air refueling for a decade after the country retired its older fleet of tankers in 1997.

An aging fleet of C-130 Hercules aircraft used in tactical refueling to CF-18 fighters is seen as inadequate.

Experts say Canada's lack of preparedness for an effective refueling program will limit its ability to contribute to international missions.

Debate over the F-35s' refueling capacity and compatibility with Canada's existing systems has raged since last year.

Liberal industry critic Marc Garneau accused the government of "forgetting" about the need to be able to refuel the fighter jets in the air during long flights and warned Canada might have to spend hundreds of millions on new equipment.

"It is getting more expensive every day. Today we discover that this plane cannot be refueled except by paying hundreds of millions of dollars more," Garneau said in Parliament. "How many hundreds of millions more and what else has the government forgotten to factor in?"

The government denies the F-35s will lack a compatible refueling capacity.