Bernie Sanders May Be Taking More Rides on Private Planes This holiday, Sanders changed his routine and almost exclusively flew private.

 -- Bernie Sanders has entered a new stage of his campaign. The Vermont senator, who is running for president on a populist message and often speaks passionately about environmental issues, was for months regularly seen flying in coach class on commercial flights.

There is even a community of photos on Twitter, under the hashtag #SandersOnAPlane, where fans have posted photos after seeing him fly. There will likely be fewer photos of a luggage-wielding Sanders moving forward.

This holiday season, Sanders changed his routine and flew almost exclusively on private chartered planes with members of his traveling staff -- taking at least four trips.

Most recently, the campaign confirmed, a Gulfstream 200, took the Senator and some staff from Burlington, Vermont two days after Christmas and then from Las Vegas, Nevada to Moline, Illinois for campaign events in eastern Iowa this week.

Days before the holiday, a private jet whisked the team from Omaha, Nebraska to Chicago, Illinois in order to fit more campaign events into this tight schedule.

Sanders flying commercial in October:

ABC News asked Sanders about whether the extremely high per-person carbon footprint of private planes was consistent with his staunch environmental policies. Sanders often talks about the need for “bold” action on climate change and even criticized the recent international Paris Accord for not going far enough to curb carbon emissions.

“The carbon footprint? As opposed to what?” the 74-year-old Senator said recently. “We are trying to get around Iowa and get around the country as best we can. So we have a lot of people to see and that is the best way can do it.”

His campaign spokesman Michael Briggs told ABC News in a statement: “Bernie is running for president of the United States and his campaign requires him to travel to many communities in Iowa and New Hampshire and other places as efficiently as possible to meet voters and to answer their questions.

“While he has used commercial airlines on almost all occasions, there are circumstances when using charter airplanes is the best way for him to get around the country and communicate with as many people as possible.”

The owner of private plane the campaign most recently used could not be reach for comment for this story, but several charter plane companies provided price estimates for similar flights ranging from $3,000-$15,000.

Many other candidates, including former Secretary of State Hilary Clinton have frequently used private planes during this campaign.