Michael Byers holds the Canada Research Chair in Global Politics and International Law at the University of British Columbia

Sometimes, a well-placed snowball can cause an avalanche.

Canada's military leaders are clearly worried that a change of government could lead to an open competition to replace our three-decade old CF-18 fighter jets. That's the most plausible explanation for the generals' effort – exposed by the leak of a classified Pentagon document last week – to conduct a rush purchase of four F-35s.

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By acquiring a handful of the stealth jets now, they seek to take Canada down a one-way road with just one possible outcome. The aim is to create what social scientists call "path dependency", not so much by the planes themselves, but the expensive training and infrastructure they require.

Canadian pilots would require extensive training for the F-35, with its unique head-up display helmet and nine million lines of software code. Most of that training would be conducted in an expensive simulator, which Canada would have to buy.

Mechanics would have to be trained in entirely new technologies, including stealth materials and a complex array of optical sensors that feed directly into the helmet.

The new planes would require highly specialized hangars. While on the ground, F-35s use 270 volts of direct current (DC), rather than the 400 Hertz of alternating current (AC) used by CF-18s.

DC cables are fragile and, for this reason, usually quite short. Each F-35 hangar built in the United States has its own power converter and subterranean service pit, from where a cable is connected to the plane. Extensive safety protections are built in, because of the considerable risk posed to mechanics by the use of DC power.

The maintenance of F-35s requires compressed air that is dryer and more highly pressurised than the air used on CF-18s. Special compressors would have to be installed in Canada's new hangars, with underground trunk lines leading to the planes.

A fighter jet fleet of any size requires a full complement of spare parts, since it is impossible to predict which parts will fail. Parts could be flown in from the United States as required, but only at the expense of valuable training time. In the United States, the high maintenance F-35s are already referred to as "hangar queens."

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Even a training fleet of four F-35s would require modifications to at least one of Canada's Polaris in-flight refuelling planes, since the couplings used to connect F-35s to tankers are different from those used for CF-18s. Modifying just one tanker would cost more than $100-million.

The final proof of the generals' strategy to commit Canada to a full fleet of F-35s is found in the extra cost of making an advance purchase of four planes.

According to the Pentagon document, Canada is requesting the four F-35s from a production lot that is due for delivery in 2015, in return for giving up four places in a production lot due in 2017. However, F-35s at this early stage in the development cycle cost more than $160-million (U.S.) each, which is more than twice the $75-million that has long been projected by the Harper government.

The discrepancy is explained by an anticipated "learning effect" whereby the experience accumulated by producing the same equipment year after year leads to efficiencies and therefore reduced costs. By purchasing the four F-35s now, the government would forgo the benefits of the learning effect – and pay at least $340-million more for the planes than it was expecting to pay in 2017.

That's a lot of money for a test drive. Indeed, it could only ever make sense if the four jets were part of a necessary transition to a full fleet of the same model of plane.

Before last week's leak, the generals were poised for a fait accompli. As the Pentagon document explains, "Canada needs to deliver Letter of Intent with updated bed down plan to F-35 (project engineering office) – (estimated completion date) mid-November." The document also indicates that US officials have initiated the process of notifying Congress about Canada's accelerated purchase.

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All of which raises an important question. Did Stephen Harper know about the plan to commit his and future governments to the F-35? Or was the prime minister – like the rest of us – about to be rolled?