Prime Minister Stephen Harper is defending his beleaguered defence minister, saying the $3 million Peter MacKay has racked up on flights aboard Challenger government jets is low compared to his predecessors.

During question period on Thursday, Harper said that MacKay has used government aircraft 70 per cent less than previous defence ministers. And when he has done so, it has been "for important government business" such as to attend repatriation ceremonies for soldiers killed in Afghanistan.

"Half of those flights are for repatriation ceremonies so that he can meet the families of those who have lost their loved ones in the service of this country. He goes there to show that we understand their sacrifice, we share their pain and we care about them," Harper said.

However, documents show that only nine of 35 flights were for repatriation ceremonies. Other flights were for press events and other political announcements.

Harper's comments came after a probe by CTV News found that MacKay has racked up nearly $3 million worth of flights on the government Challenger jets since he became defence minister in 2007.

MacKay's office has defended the flights, saying the minister has used the jets for official business.

The CTV investigation revealed that the defence minister has logged the most flyer miles aboard the government's fleet of Challengers than any other minister. Flight logs indicate that MacKay has flown a total of 247 hours aboard the aircraft, far more than his counterparts at Foreign Affairs and Finance.

In 2009, MacKay flew 96 hours aboard the Challenger, compared to 59.5 hours for Finance Minister Jim Flaherty, and 27.6 hours for then-foreign affairs minister Lawrence Cannon.

Earlier on Thursday, Ethics Commissioner Mary Dawson said that MacKay may have breached conflict of interest rules when he vacationed at a fishing lodge owned by a Crown corporation board chair.

The trip in question took place in July 2010. CTV News reported last week that MacKay was picked up from the vacation by one of only three search-and-rescue helicopters available in Newfoundland.

Dawson made the comments while speaking before a session of the Standing Committee on Access to Information, Privacy and Ethics. During the session, Liberal MP Scott Andrews asked Dawson about MacKay's stay at the Gander River fishing camp, which is owned by Marine Atlantic Chairman Rob Crosbie.

Andrews asked Dawson if the vacation represented a potential breach of ethics.

Dawson replied that "there could be contraventions in those areas."

During Thursday morning's session, Andrews first asked the commissioner if she has "looked into investigating" the trip. She replied that she had only seen press reports about MacKay's vacation.

When Andrews asked if she would launch an investigation herself, Dawson said she would have to receive a request to probe a specific incident, "and there has to be reasonable grounds of a specified provision that had been contravened."

Andrews later told Dawson that "that is maybe something we could formalize in a formal request."

The Department of National Defence has three Cormorant helicopters based out of Gander, N.L., which are expected to cover a massive region of eastern Canada 24 hours a day.

MacKay's office defended the pick-up, calling it an opportunity for the minister to view a rescue demonstration.

"After cancelling previous efforts to demonstrate their search-and-rescue capabilities to Minister MacKay over the course of three years, the opportunity for a simulated search and rescue exercise finally presented itself in July of 2010," a statement from MacKay's office said.

"As such, Minister MacKay cut his personal trip to the area short to participate in this Cormorant exercise."

Military sources told CTV News, however, that no such exercise was planned until MacKay's office requested the pick-up.

The total annual cost per flying hour to operate a Cormorant is $32,232.