Defence Minister Harjit Sajjan is a frequent flier on government jets, racking up more than $670,000 in costs in a 17-month period and far surpassing cabinet colleagues, travel records show.

Prime Minister Justin Trudeau and recently retired governor-general David Johnston flew the most on Defence Department aircraft over the past two years, but they are not allowed to travel on commercial aircraft for security reasons.

Mr. Sajjan, who is in charge of the Challenger and Airbus jets operated by the Department of National Defence, does not have the same security requirements as the Prime Minister.

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Flight logs for 2016 and the first five months of 2017 show Mr. Sajjan took 20 trips on Challenger aircraft from January, 2016, to May, 2017, at cost of $670,692. These flights comprised more than 206 hours of flying time.

These are not flights in which the Defence Minister was merely a passenger, but ones where he is listed as the requisitioning minister.

Logs are now only available up to May, 2017.

"He is taking the jets because he wants to take the jets because he doesn't want the hassle of mixing with ordinary people," NDP ethics critic Nathan Cullen told The Globe and Mail. "We are not able to provide our troops with the proper equipment and this will be pretty offensive to a lot of our men and women in uniform."

The price tag for the trips as reported by the military does not include the full cost of operating the planes.

Mr. Sajjan's trips over the past two years would exceed $3-million if all costs, including fixed costs, such as crew salaries and the amortized cost of the aircraft, are included in the tally.

The military says it's not accurate, however, to price the trips using the National Defence Department's full cost accounting for CC-144 Challenger jets – currently pegged at $14,891 a flying hour – because these include costs that are incurred regardless of whether the flights took place.

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No other cabinet minister has requisitioned anywhere near the number of flights on DND government aircraft as Mr. Sajjan. The post of foreign affairs minister, for instance, requires heavy international travel. But logs released to the media show former foreign affairs minister Stéphane Dion requisitioned it only once; Foreign Affairs Minister Chrystia Freeland does not show up as a requisitioning minister in the period released.

Finance Minister Bill Morneau requisitioned the Challenger jets four times between January, 2016, to May, 2017 – as did Fisheries Minister Dominic LeBlanc.

Justice Minister Jody Wilson-Raybould, Environment Minister Catherine McKenna, International Development Minister Marie-Claude Bibeau, International Trade Minister François-Philippe Champagne and National Revenue Minister Diane Lebouthillier each requisitioned one flight. Transport Minister Marc Garneau and Agriculture Minister Lawrence MacAulay together requisitioned one flight.

A spokeswoman for Mr. Sajjan said he tries wherever possible to use commercial fights because the Liberal government is committed to "responsible use of taxpayer dollars."

In 2017 so far, according to Mr. Sajjan's press secretary, Byrne Furlong, the Defence Minister has flown approximately 140 times on commercial airplanes as compared with 18 times on government aircraft.

Flight logs released to media show three instances in 2017 where the Defence Minister opted to fly the Challenger jet to Andrews Air Force Base near Washington, even though commercial airlines offer regular daily flights to the U.S. capital. Using the military's accounting, a round trip from Ottawa averages about $9,500.

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"I booked a flight to Washington last year for $300," Mr. Cullen said. "I mean, it is an hour. It is not like you are being inconvenienced and having to fly to South Korea."

Mr. Sajjan's office said government aircraft are employed "when circumstances do not allow for commercial travel."

In February, 2017, Mr. Sajjan was the lone passenger on a Challenger jet flying from Ottawa to Washington and then on to his home in Vancouver. The cost: $36,605.

In an e-mail, Ms. Furlong said the minister flew to Vancouver to meet with "high-level business leaders.

"Minister Sajjan hosted a roundtable discussion in his capacity as Minister of Defence with private sector leaders to discuss defence priorities, conflict prevention, innovation and strengthening the private sector's role in defence engagement."

Ms. Furlong said the Defence Minister flew on a government plane that day because the schedule called for bilateral discussions with U.S. Defence Secretary Jim Mattis in Washington "followed by an engagement in downtown Vancouver that same day with private sector leaders to discuss defence priorities and innovation."

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"Given the importance of our relationship with the United States, we often travel between the capitals. It is important to note that often we must travel in the mornings, and flights are not always available at this time due to ministerial commitments in Ottawa," Ms. Furlong said.

Mr. Sajjan also used the Challenger jet for overseas travel, flying from Ottawa to Copenhagen at a cost of $61,000 in May, 2017. In May, 2016, the minister flew from Ottawa to Stuttgart, Germany, and back to Ottawa. The price tag was $52,454. A month later, it cost taxpayers $49,910 to fly Mr. Sajjan between Ottawa and Brussels.

Overseas flights require a stopover in locations such as Gander, Nfld., to refuel.

On one occasion in December, 2016, Mr. Sajjan opted to fly from Ottawa to the Trenton, Ont., military base rather than drive about 2 1/2 hours in his government limousine. The cost of flying to Trenton was $6,358.

Flight records show Mr. Trudeau used government aircraft more than 70 times between January, 2016, and May, 2017, and the governor-general flew on them on more than 40 times.

Former Conservative defence minister Peter MacKay was a frequent flier on government jets during the Harper era. Logs released to the media over a four-year period, 2008 to 2011, recorded 35 trips arranged for Mr. MacKay comprising nearly 250 flying hours.