Taylor Swift's lawyers have threatened legal action against a student who tracks the movements of her and other celebrities' private jets.
Jack Sweeney is the creator of social media accounts that log the takeoffs and landings of planes and helicopters owned by billionaires, politicians, and other public figures.
His accounts gained traction at the start of Russia's 2022 invasion of Ukraine for tracking the private jets of Russian oligarchs.
The University of Central Florida student said on Tuesday that he had received a cease and desist letter from Swift's lawyers, who have described his actions as "reckless" and said the singer lives her life "in a constant state of fear for her personal safety".
"While this may be a game for you or an avenue that you hope will earn you wealth or fame, it is a life-or-death matter," the 14-time Grammy winner's lawyers wrote in the letter, provided by Mr Sweeney to NBC News - the US partner of Sky News.
It comes after a Seattle man, David Crowe, was arrested two weeks ago for allegedly stalking Swift outside her townhouse in New York City.
Swift's lawyers have accused Mr Sweeney of "stalking and harassing behaviour" in the letter - an allegation the student's own lawyers have firmly rejected.
According to Mr Sweeney, the accounts are aimed at providing "transparency" and use publicly available data from the Federal Aviation Administration.
"I think it's important to note that nowhere do I intend for harm, I simply share the facts," he told NBC News.
"I actually think Swift has some good songs."
James Slater, a Florida lawyer who is representing Sweeney, said Swift's legal team had no legal authority to block the accounts.
"There's no claim to just publicising public information," Mr Slater said.
"And in Ms Swift's lawyers' letter, they didn't address any real claims."
Sky News has contacted Swift's representatives for comment.
It comes as the singer could be days away from making one of the most closely watched private jet journeys in recent world history.
The 34-year-old star is about to play four nights at Japan's Tokyo Dome.
The last of the gigs is set to take place on Saturday night - one day before her boyfriend Travis Kelce and his Kansas City Chiefs play the San Francisco 49ers in the Super Bowl in Las Vegas.
Experts say Swift could complete the gig and arrive in Las Vegas with enough time to attend the game, if she makes the journey in her private jet.
Swift has faced criticism over the carbon footprint from her use of private jets, though her representatives have previously stated that she uses offsetting through the purchase of carbon credits to compensate.
"Taylor purchased more than double the carbon credits needed to offset all tour travel," her publicist said before the start of her recent Eras Tour.