“Private jets are the biggest source of aviation emissions.”

Two 2024–2025 studies frame the numbers. A Nature-family paper tracking 18.6 million private flights put 2023 emissions at about 15.6 million tonnes of CO2, up 46% since 2019, equivalent to around 1.8% of commercial aviation. The International Council on Clean Transportation's 2025 analysis, using a broader scope, estimated up to 19.5 million tonnes — more than every flight departing Heathrow that year — and noted that private jets' share of civil-aviation emissions peaked near 4% during the pandemic when airlines were grounded.

Against the total: commercial aviation emitted roughly 900 million tonnes of CO2 in 2023, and aviation as a whole accounts for about 2.5% of global energy-related CO2. Private jets are a small slice of a modest slice.

The per-person picture is what drives the outrage. A mid-size jet burning 200–300 gallons an hour with four people aboard emits far more per passenger than an A320 with 180. Studies estimate private flyers' aviation emissions at up to 500 times those of the average person. Many private flights are short — under 500 km — where rail is an option, and a substantial share fly empty on repositioning legs.

So 'biggest source' is wrong, 'most carbon-intensive way to fly' is right, and the industry's own sustainability pledges accept the second point.