Jack Sweeney, 20, has become an unexpected authority on the flight paths of the rich and famous. When Kylie Jenner’s Bombardier BD-700 flies from Van Nuys, Calif., to nearby Camarillo, or Taylor Swift’s Falcon 7X takes off in Nashville, Sweeney’s Twitter bot @CelebJets shares the private jet’s whereabouts, flight duration and estimated carbon emissions.

“ ‘You can show up 15 minutes before, five minutes before. You can show up late, and the plane will wait for you.’”

With his tweets, Sweeney, a sophomore at the University of Central Florida who also runs the Elon Musk jet-tracking account @ElonJet, has propelled a global conversation about the role celebrities play in the warming of the planet. After @CelebJets shared that Jenner’s plane had completed a 17-minute flight in July, she was branded a “climate criminal” by online commenters. And for several weeks now, Swift’s jet has been the subject of memes about needlessly flying private: to Starbucks SBUX, -1.84%, Target TGT, -3.47%, the fridge. 

A spokesperson for Swift said, in an email, “Taylor’s jet is loaned out regularly to other individuals. To attribute most or all of these trips to her is blatantly incorrect.” Jenner declined to comment through a representative. 

Sweeney said he hopes that his @CelebJets account, which has 112,000 followers and relies on public data gleaned from a network of ground-based receivers, will push private fliers “to be more efficient.” So far, they have primarily stoked outrage among climate-conscious millennials and Gen Z–ers.

“ ‘I’ve been in the private jet market for the last 10 years, and on the aviation commercial side for 22, and I’ve never seen the private-jet business like this.’”

After Jenner shared a photo to Instagram of her and rapper Travis Scott’s private jets (caption: “you wanna take mine or yours ?”), fans condemned the post as a display of excessive wealth and environmental indifference. “Eat the rich” and “tax the rich” were common refrains. “Girl what am i recycling for,” another commenter wrote. 

An expanded version of this report appears at WSJ.com.

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