Bernie Sanders took a private jet to the Vatican to address a conference on wealth inequality on Friday, hours after attacking Hillary Clinton over her stance on fossil fuels.
The Democratic candidate is believed to have flown with fewer than 50 people aboard the Delta 767, a jet that can carry between 211 and 261 people.
Joining him on the more than 8,500-mile round trip flight were his wife, Jane, and 10 family members, including four grandchildren.
The whole trip would have used up to 33,193 gallons of fuel, calculated MailOnline, which noted that an average American - who is estimated to fly only 7,500 miles per year - releases fewer carbon emissions via aircraft in 12 months than Mr Sanders did for the trip to Rome.
Hours earlier during the Democratic debate, Mr Sanders claimed some of Mrs Clinton's support came from employees at oil companies and lobbyists for the fossil fuel industry. "'As I understand it, 43 lobbyists for the fossil fuel industry maxed out, gave the maximum amount of money to Secretary Clinton's campaign," he said.

He also claimed to have "introduced the most comprehensive climate change legislation, including tax on carbon" - something, he said, Mrs Clinton did not support.
Addressing the Vatican conference, Mr Sanders issued a global call to action to tackle "immoral and unsustainable" wealth inequality and poverty, using the high-profile gathering to echo one of the central platforms of his presidential campaign.
The Democratic senator from Vermont cited Pope Francis and St. John Paul II repeatedly during his speech to the Vatican conference commemorating the 25th anniversary of a landmark teaching document from John Paul on social and economic justice after the Cold War.
The trip to the Vatican gave him a chance to expand on his core campaign messages about the need to reform banking regulations, campaign finance rules and higher education. Asked about inequality in public education, he said it was "beyond disgraceful" and cited challenging conditions in Detroit's school system.

He told the audience that rather than a world economy that looks out for the common good, "we have been left with an economy operated for the top 1 percent, who get richer and richer as the working class, the young and the poor fall further and further behind".
"We don't choose to politicise the pope," Mr Sanders told attendees, "but his spirit and courage and the fact, if I may say so here, that his words have gone way, way, way beyond the Catholic Church".
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