Canada's chief of defence staff defended his use of government-owned Challenger jets Monday and said he respects taxpayers' money.

Media reports released last week said Gen. Walter Natynczyk used government planes to travel to fundraisers, football and hockey games and to join his family on a cruise in the Caribbean.

Speaking in the foyer of the House of Commons, Natynczyk said his role requires him to travel extensively, across Canada and internationally and that his schedule is sometimes "relentless." He has said he was using the jets to travel to and from events where he was representing the military.

The Prime Minister's Office has said it would look into the expenses and Natynczyk said if he's advised he must pay back some money, he would.

Natynczyk met with Prime Minister Stephen Harper and opposition defence critics Monday morning. He says he has the full support of Harper and Defence Minister Peter MacKay.

Challengers 'not used very much'

Last week's news reports indicated that it costs about $10,000 an hour to fly a Challenger, including pilot salaries, training costs and the cost of the planes' depreciation. The actual flying cost is $2,630 an hour, according to numbers provided by the Department of National Defence.

"These aircraft — these Challengers — are not used very much," CBC's James Cudmore reported.

Natynczyk said military Challengers are flown an additional 170 hours a year with no passengers on board so that pilots can maintain their proficiency.

"So these hours are paid for, they're all paid for — there's no incremental cost to the Crown," he said. "That's why, especially when I travel and I have the team with me, it's less expensive to the government of Canada to get into that Challenger than it is to put them into an aircraft, in a commercial aircraft."

Natynczyk travels with up to six or seven people, sometimes including a close protection team with automatic weapons. He also needs the secure communication lines provided on government aircraft that allow him to work while he's in the air.

Cudmore said sources told CBC News that the story about Natynczyk may have been leaked by someone, perhaps in a bid to see the general replaced.

Asked whether somebody's out to get him, Natynczyk said he's developed a thick skin.

"I’ve served in some pretty war-torn locations. I’ve been shot at in Sarajevo, I’ve been shot at in Baghdad. I’ve got some pretty tough skin right now and I just continue to serve," he said.

Hung out to swing

Liberal defence critic John McKay says Natynczyk made a compelling case.

"If the plane is sitting on the ground, nothing's happening with the plane. It’s still a cost to the taxpayer and the irony of the whole thing is that if he in fact books a commercial flight, it’s actually adding to the cost to the taxpayer," McKay said, adding he's critical of the NDP and Harper.

"I think they should have done the general a courtesy of phoning him up and asking him to give some coherent explanation to these costs. Otherwise he’s just hung out in the public realm to swing."

'Respectful of the taxpayers' dollar'

Natynczyk said he uses many forms of travel, including commerical airlines, and he's always mindful of expenses.

"I'm trying to go out with the most efficient means of transportation, being very respectful of the taxpayers' dollar," he said.

"There is this notion that Challenger flights are more expensive. I work within the budget that we have allocated to all of our fleets," he said.

One of the Challenger trips cited in last week's media reports was a 2010 flight to join his family on a Caribbean vacation. Natynczyk said he was preparing to go on vacation with his family after spending Christmas in Kandahar. As he was about to leave for vacation, four Canadian soldiers and Alberta journalist Michelle Lang were killed by a roadside bomb.

Natynczyk said he sent his family on without him so he could attend the repatriation ceremony in Trenton, Ont. After that, MacKay offered him the use of the plane so he could catch up with his family.

Government 'dramatically cut' use of jets

On Friday, Harper said officials who use the jets for personal reasons should write a cheque to Ottawa. 

Harper said the current government has "dramatically cut the use" of government aircraft.

"Cabinet members only use government aircraft when it is required, when they are required to travel and commercial options are not feasible or available for them," he told reporters in Saskatoon

But CBC News has learned the Prime Minister's Office appears not to follow that rule.

In February, Harper travelled by Challenger to Washington, D.C., to meet with U.S. President Barack Obama. Flight logs obtained by CBC News show there were eight people aboard the Challenger, including Lawrence Cannon, then foreign minister, communications director Dimitri Soudas and several staff members.

The flight logs also indicate a second Challenger was used to fly nine more staffers, including three more press aides, a speechwriter, a photographer and videographer to Washington.

The second Challenger left Ottawa for Washington 14 minutes before the prime minister's plane and returned to Ottawa later that day, just five minutes after the prime minister's flight touched down. 

With files from CBC's James Cudmore