One unusual accident during a routine training exercise underlines the fragility of Canada's Pacific navy fleet.

The two aging ships damaged in a collision at sea happen to be the most crucial vessels for blue-water naval operations in the Pacific. Until repairs are completed, the fleet that's based on Canada's West Coast is missing its sole destroyer and it doesn't have a supply vessel to re-fuel ships at sea.

The mishap, in the eyes of some analysts, puts the spotlight on a flaw in the Conservative government's plans to replace Canada's Royal Canadian Navy fleet. Even after long delays, Ottawa is only planning to buy one supply ship for each coast, leaving the Navy vulnerable to an accident.

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The two ships in the recent incident, the destroyer HMCS Algonquin and supply ship HMCS Protecteur, collided when they were conducting a routine towing exercise en route to Hawaii. There were no injuries, but the Royal Canadian Navy is assessing the damage to both ships while it convenes a board of inquiry to determine what went wrong.

One thing that's clear is that the fleet – which includes five frigates, six smaller patrol ships, and one submarine – will have a few gaps, at least for a while. The commander of the Pacific fleet, Commodore Bob Auchterlonie, told Canadian Press that it's not clear yet how long.

The holes are significant for a navy with some ships verging on the elderly – Algonquin was commissioned in 1973, and Protecteur in 1969. Protecteur is one of two surviving Canadian supply ships, the so-called "oilers" that re-fuel other ships at sea, which remain in service because of a decade of delays in plans to replace them. Even now, only a design for the replacements has been selected, and the ships won't be built until at least 2018.

Critically, instead of the originally planned order of four, Ottawa is now expected to buy just two – one for each coast. That means Canada's future Navy could still be hobbled by a simple accident like the collision between Algonquin and Protecteur.

"One thing it does demonstrate is the vulnerability of only having two," said David Perry, a senior analyst with the CDA Institute.

Without a supply ship, the Canadian Navy cannot dispatch a task force across the Pacific – unless it relies on an ally for refuelling, or makes pit stops in ports.

Without HMCS Algonquin, the Pacific fleet also does not have a destroyer – the biggest and most heavily armed warships in the Royal Canadian Navy. There are three destroyers in the navy, but two are based in the Atlantic, and only one, the Algonquin, in the Pacific.

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That, too, stems from a historic priority for the Atlantic that some believe is now outdated. The Royal Canadian Navy splits its ships unevenly between the two coasts, with the Atlantic given a slightly larger fleet – seven of 12 frigates are stationed there.

Now that the United States has announced a "pivot" to Asia to emphasize its military presence there, and disputes over islands and maritime claims have increased naval activity in the Pacific, some argue that Canada should shift, too. "I haven't seen anything from the government of Canada to direct the Royal Canadian Navy to take a greater role there," Mr. Perry said.