NEW YORK (NYTIMES) - For Elon Musk, the billionaire chief of Tesla and founder of SpaceX, travelling by private jet is not such a private endeavour.

Jack Sweeney, 19, a freshman at the University of Central Florida in Orlando, has been tracking a Gulfstream G650ER that he identified as Musk's private jet and posting maps of its whereabouts on a popular Twitter account since June 2020.

Musk is not the only famous person being followed by the pesky wingman, who has thwarted efforts by Musk and others to cloak their movements on aircraft-tracking applications and websites.

The nosy can also keep up with Drake, Mark Cuban, Jeff Bezos and Bill Gates on Sweeney's other accounts.

Sweeney said on Wednesday (Feb 2) that he was able to track them using data from their plane's transponders - a public record that includes the aircraft's altitude, latitude and longitude and heading - an algorithm and a bot that he created.

But Musk was rather vexed by the flight-tracking gambit, Sweeney recalled in an interview, saying that he received a direct message on Nov 30 from the billionaire on Twitter asking him to deactivate the account @ElonJet.

"I go like, Oh, my gosh, Elon Musk just DM'd me: 'Can you take this down? It's a security risk,'" Sweeney said. "Then he offered me US$5,000 (S$6,720) to take it down and help him make it slightly harder for 'crazy people to track me.'"

Sweeney provided screenshots of the exchange to The New York Times, which was not able to independently verify its authenticity.

Musk did not immediately respond to messages seeking comment on Wednesday, including to say whether he sent the messages.

The exchange highlighted the tension between open public records and privacy - and it was not the first time famous people had been tracked. Journalists have used flight-tracking apps to follow politicians before vice-presidential selections. Investors use them to shadow CEOs to get wind of corporate mergers. Sports fans have used them to track coaching candidates of their favourite teams.

Cuban, the billionaire owner of the Dallas Mavericks, declined to comment on Wednesday. Representatives for Bezos, the Amazon founder; Gates, one of Microsoft's founders; and Drake, the hip-hop mogul, did not immediately respond to requests for comment on Wednesday.

Ryan Calo, a law professor at the University of Washington whose focus is technology and its legal implications, said Wednesday that the Federal Aviation Administration (FAA) required planes to transmit location data to prevent collisions and to help find lost aircraft.

"What this teenager is taking advantage of is a lack of foresight on the part of the FAA that this would become a privacy problem for some people," Calo said.

Reached for comment on Wednesday, the FAA said that the situation was outside the agency's scope of authority.

Calo was amused that a teenager would hear directly from Musk.

"There almost couldn't be a greater power asymmetry between Musk and this teenager," Calo said. "This is not David and Goliath. This is like Goliath and a flea on David."

Sweeney said that he was drifting off to sleep when his Android phone buzzed at 12.19am on Nov 30. He had been in his dorm room, where several posters promoting SpaceX, Musk's space exploration company, were hanging on the wall above his bed, according to a photograph shared on Sweeney's personal Twitter account.

Sweeney made a counteroffer to Musk, according to the screenshots of the exchange, saying that he would abandon the account if Musk upped the ante to US$50,000. He said that he would also accept a Tesla Model 3, an electric car that costs more than US$38,000, adding that he was joking.

In the exchange, Sweeney was asked how he had been able to track Musk. He explained that he had obtained the plane's transponder data. When told that paying to have the Twitter account shut down did not seem right, Sweeney made another proposal: How about an internship?

The exchange, which carried on for more than a month, went silent after Jan 23.

Sweeney downplayed the privacy and security concerns associated with his tracking account for Musk, which has more than 305,000 followers.

"It's a private jet, so he goes right from the jet to the car," he said, adding that he has long been fascinated by tracking planes. "I don't think it's that big of a concern. Some people are just interested in seeing where he goes."

Sweeney said that he obtained the data for his aircraft-tracking accounts from the ADS-B Exchange, which describes itself on its website as the world's largest source of unfiltered flight data.

Dan Streufert, the founder of ADSBexchange.com, said in an email on Wednesday that anyone with basic electronics could obtain the signals from aircraft that broadcast their locations. The information is also available by listening to air traffic controllers, he added.

"However, it is important to note our website tracks aircraft, not individuals," Streufert said. "We cannot say who is or is not on the plane. Mr Musk's companies own and operate many aircraft - this is only one of them. Mr Musk may find Mr Sweeney's activities annoying, similar to paparazzi, however, this information is already public from a myriad of sources."

Calo said that as long as Sweeney did not create the flight-tracking accounts to demand money from Musk and others, it would be difficult to make a criminal case that it was extortion.

"You'd have to purposely create this harm and hold it over somebody," he said.

Calo said that it would be difficult for a public figure like Musk to bring a civil lawsuit against Sweeney contending that his privacy had been breached.

"So I think there would be real hurdles to try to pursue this kid, civilly," he said.

Still, he cautioned that Sweeney could open himself up to litigation if he took it too far.

"That's quite a ride," he said. "He just has to proceed carefully from here."

After Sweeney's last message to Musk on Jan 23, the exchange bore a certain finality.

"You can no longer send messages to this person," an automated message from Twitter read.