Prime Minister Jean Chretien says he's not embarrassed by the grounding of Canada's fleet of Sea King helicopters.

The prime minister's comments come a day after the Air Force announced its fleet of Sea Kings is being restricted to essential mission flights only, after two of the aircraft recently lost power while hovering. It's the first time the fleet's flying time was restricted in its troubled 40-year history.

In both incidents -- neither of which were reported publicly -- crews were able to recover and successfully land the aging copters.

Opposition Leader Stephen Harper told Parliament Thursday that Chretien should be ashamed of allowing the military to use the outdated choppers.

"Of all the embarrassing legacies of this government, perhaps the worst is in national defence. Today we have the entire Sea King fleet grounded," Harper said.

He honed in on the Chretien government's decision to cancel a multibillion-dollar order to replace the Sea Kings 10 years ago.

"Isn't the prime minister embarrassed to be leaving office after a decade with no replacements for the Sea King?" Harper asked.

Chretien replied he wasn't embarrassed at all by six consecutive balanced budgets.

"Those helicopters were not replaced, but the same type of helicopter is used by the president of the United States to go from the White House to Camp David," Chretien said.

"So, I presume that if it's a good enough helicopter for the president of the United States, it should be a good enough helicopter for the Canadian soldiers."

The choppers are not permitted to conduct routine training missions, but can still respond to emergencies.

Investigators are now examining the engines and gear boxes on two Sea Kings. If engineers find enough similarities between the two mishaps, they could decide on a complete grounding of the fleet.

"If the incidents were linked it might point to a broader fleet-wide issue,'' Lt.-Col. Bruce Ploughman, operations officer of the Sea King fleet at Halifax's Shearwater base, said Thursday.

Lt.-Col. Dave Mason, commanding officer of the fleet's flight maintenance, said specialists were zeroing in on the fuel content, the fuel delivery to the engines, and the performance of the engines and gear boxes.

They were also looking at the way the engines and gear boxes were installed and maintained, since both helicopters came from the same hangar and might have been subject to flawed service.

There was no indication of how long the inspections would take.

Canada's 28 Sea Kings were purchased in the 1960s and have been plagued over the years by mechanical failures, parts shortages and crashes. Over the years, there have been four fatal crashes that killed 10 people.

The latest high-profile crash occurred Feb. 27 when one of the aircraft suffered engine failure on takeoff and slammed onto the deck of HMCS Iroquois, injuring three crew members.

A replacement helicopter had to be shipped to the Persian Gulf by commercial freighter.

Chretien's Liberal government has said it plans to buy replacements for the Sea Kings, but a long and convoluted contract process has dragged on for years.

Frequent mechanical breakdowns keep Canada's Sea Kings in the shop 30 hours for every one hour of flight.