The total cost per flying hour for a C-17 is $21,239. It is not known how many hours were required for the trip or how many stops were involved.

The prime minister was driven around in a black Chevy Suburban SUV with Ontario plates at his first stop in Agra, India. A second Canadian car, a black Cadillac sedan, met him on his arrival in New Delhi.

Asked for the reasons behind the decision to ship the vehicles to India from Canada, the Prime MInister's Office referred all questions to the RCMP. The Mounties issued a brief statement later Monday morning.

"The deployment of RCMP resources are dictated by operational requirements, including public and officer safety considerations, and a threat assessment of the events/environments," said Cpl. Lucy Shorey in the statement.

"For security reasons, details on the security plans will not be discussed."

Ray Boisvert, former assistant director of intelligence with the Canadian Security Intelligence Service and now president and CEO of I-Sec Integrated Strategies, said the RCMP's threat assessment would be carried out in cooperation with other agencies such as CSIS and Indian police - and that elements flagged in the "threat matrix" likely warranted enhanced security measures.

While it is a democratic country, India has a long history of deep religious and ethnic strife and has been the location of many bombings in past, he said.

"India represents probably the best possible example of a theme park of domestic threats - it covers the whole spectrum of still some violent groups of Maoist, extreme left, to Islamic extremism," Boisvert told CBC News Network's Power & Politics host Evan Solomon Monday.

"There's a number of issues, probably a lot of reasons why the RCMP, at least the officer in charge, probably took a deep, long look at the threat assessments and decided to go with the best possible safety piece."

Vehicles have varied on past trips

The prime minister has used his own cars on foreign visits before, in Haiti and Afghanistan. On his recent trip to Kinshasa, Congo, Harper was driven around in a silver Toyota 4Runner, which did not appear to be Canadian.

On a trip to India such as this, Harper would normally have been travelling in a Hindustan Motors Ambassador car, a vintage-looking white sedan, several of which were seen in Monday's motorcade.

The U.S. president uses his own armoured vehicles on foreign trips flown in for the occasion, as Barack Obama did on his first official trip to Canada in 2009.

The prime minister's spokesman, Andrew MacDougall, told reporters on the tour the full price of the security measure will be disclosed when it's available.

"I don't have the costs in front of me. We won't know that for a while," he said.

NDP finance critic Peggy Nash raised the issue during the House of Commons' question period Monday, asking: "How much is it costing to send the prime minister's personal limousines to the Taj Mahal?"

Public Safety Minister Vic Toews repeated that the RCMP made the call, adding "I trust their judgment."

India has a history of terrorist attacks and political assassinations - including that of its own prime minister Indira Gandhi in 1984. In 2008, a series of attacks on a number of locations in Mumbai, including a luxury hotel, killed 166 people.

with files from Terry Milewski, James Cudmore and The Canadian Press