FIRST ON FOX: Environmental groups that have been vocal about climate change were silent when asked about Vice President Kamala Harris' campaign dropping nearly $7 million on private jet flights since July.

Harris spent nearly $4 million on private flights in just six weeks starting in July, after calling on Americans to change their habits to curb climate change, a previous Fox News Digital review found.

The latest review of new filings with the Federal Election Commission reveals that Harris spent an additional $3.1 million on private planes in September alone. 

Fox News Digital asked environmental groups, several which have protested private jet use, about Harris' private flights but did not receive a response from any of them. The groups included Sunrise Movement, the Center for Biological Diversity, Greenpeace, Earth Island Institute, Earth Justice, Naturefriends International, and International Union for Conservation of Nature.

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Then-Democratic vice presidential nominee Kamala Harris exits a private plane at Fort Worth Meacham International Airport on Oct. 30, 2020 in Fort Worth, Texas.

Then-Democratic vice presidential nominee Kamala Harris exits a private plane at Fort Worth Meacham International Airport on Oct. 30, 2020 in Fort Worth, Texas. (Montinique Monroe)

Members of the Sunrise Movement held a protest at East Hampton Airport in 2023 to prevent planes from taking off and landing in opposition to private air travel.

Greenpeace has also slammed those who engage in the upscale form of travel.

"The super rich proudly accelerate the #ClimateCrisis, showing off their planet-wrecking lifestyle. Let’s stop this reckless behavior," Greenpeace writes on their website. "Private jets are the epitome of social and climate injustice: a supremely privileged minority flying like there’s no tomorrow without any restriction."

Harris used two different companies for her private flights in September: the Private Jet Services Group (PJS) and Advanced Aviation Team.

PJS offers a range of services from a light jet for groups of up to seven passengers traveling up to 535 miles per hour, or an airliner that accommodates 150 to 350 passengers.

The PJS website claims the group is America's first carbon-neutral private aviation company.

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Sunrise Movement protesters gather near Vice President Kamala Harris' Brentwood, California, home, calling on her to urge President Biden to declare a climate emergency on Sunday, April 14, 2024.

Sunrise Movement protesters gather near Vice President Kamala Harris' Brentwood, California, home, calling on her to urge President Biden to declare a climate emergency on Sunday, April 14, 2024. (Robert Gauthier)

"PJS has implemented a reforestation program to sequester 100% of the carbon emissions released by our clients’ flights. The PJS Carbon Neutrality Pledge establishes Private Jet Services as America’s First Carbon Neutral Private Aviation Company," the website reads.

Harris also used Advanced Aviation, which offers aircraft ranging from eight-seater turboprop jets for trips of up to three hours to 18-seater ultra long-range jets.

When asked whether the campaign weighs the private jet carbon footprint before taking the flights, the Harris campaign did not respond to Fox News Digital by press time.

The National Library of Medicine reports that private aviation is "the most energy-intense form of air travel" and that fuel use per passenger varies, "but [is] estimated to be on the order of 10 to 20 times higher than the average fuel use per passenger hour for a commercial flight."

Harris has previously called climate change an "existential threat" and said that human habits contribute to the issue.

Then-Democratic vice presidential nominee Kamala Harris exits a private plane at Raleigh Durham International Airport on Sept. 28, 2020 in Raleigh, North Carolina.

Then-Democratic vice presidential nominee Kamala Harris exits a private plane at Raleigh Durham International Airport on Sept. 28, 2020 in Raleigh, North Carolina. (Sara D. Davis)

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"There’s no question we have to be practical. But being practical also recognizes that climate change is an existential threat to us as human beings," Harris told CNN in 2019. "Being practical recognizes that greenhouse gas emissions are threatening our air and threatening the planet and that it is well within our capacity as human beings to change our behaviors in a way that we can reduce its effects. That’s practical."

The 2024 presidential campaign is not the first time Harris has used private jets to hit the campaign trail. In 2019, Harris' campaign spent hundreds of thousands of dollars on flights chartered by Air Partner Inc., which bills itself as a "World-class" private aircraft charter company that offers "over 7,000 private jets."

"We can give you access to every type of private jet, from very light to global cabin jets," the website reads. "You have the freedom to choose the most suitable aircraft for your journey, whether you're flying for business or leisure."