The re-election campaign for Vermont senator Bernie Sanders spent nearly $300,000 to travel on a private jet in the final stretch of the midterm election, filings with the Federal Election Commission show.

The spending on private travel was for a campaign trip Sanders did to boost far-left candidates in nine different states, his campaign spokesman said.

"This expense was for transportation for the senator's nine-day, nine-state tour to support Democratic candidates up and down the ballot ahead of Election Day," campaign spokesman Arianna Jones told VTDigger.org, which was first to identify the spending. "This cost covered the entirety of the tour from Indiana, Michigan, Wisconsin, Iowa, South Carolina, Colorado, Nevada, Arizona, California, and back to Vermont."

The Sanders campaign made a $297,685.50 payment on October 10 to Apollo Jets, a New York-based private jet service used by stars such as Derek Jeter and Shaquille O'Neill, according to its website. The company's featured jet is a Falcon 8X, it says.

His campaign made a much smaller payment of $37,567.53 to Apollo Jets in July 2017, the Washington Free Beacon reported.

Air travel is one of the biggest sources of greenhouse gas emissions, with some estimations saying that the aviation industry accounts for about 11 percent of transportation-related emissions in the country. The environmental impact is greatly magnified in cases of private flights, which carry far fewer people per trip than commercial jets.

Sanders claims on his website that "climate change is the single greatest threat facing our planet" and puts the blame chiefly on the growing rate of emissions being produced by the transportation sector.

"Global climate change is real, it is caused mainly by emissions released from burning fossil fuels and it poses a catastrophic threat to the long-term longevity of our planet," he writes. "The transportation sector accounts for about 26 percent of carbon pollution emissions."

The Sanders campaign told the Washington Free Beacon it purchased "carbon offsets" to balance out emissions produced on the trip.

"The campaign purchased carbon offsets from Native Energy to support renewable energy projects and invest in carbon reduction projects to balance out the emissions produced on this trip," Jones said in an email.

The Washington Free Beacon was unable to identify payments made by the campaign to the environmental group. Jones says the purchase will appear in the campaign's next filing.

Sanders similarly partnered with Native Energy during his failed 2016 presidential campaign.