Elon Musk was upset Bezos did not invite him to visit Blue Origin's factory, after Bezos toured SpaceX in 2004, a new book says

• Musk's SpaceX and Bezos' Blue Origin have been one-upping each other in a billionaire space race.
• A new biography of Musk says he was upset with Bezos for not receiving a reciprocal invite to tour Blue Origin's factory after Bezos toured SpaceX.

Elon Musk's SpaceX and Jeff Bezos' Blue Origin have long been locked in a billionaire space race.

In 2020, SpaceX completed its first manned spaceflight, while Blue Origin did the same — with Jeff Bezos on board — in 2021.

Now, Elon Musk's new biography, penned by Walter Isaacson after trailing him for three years and published Tuesday, sheds light on the earliest stages of Musk's relationship with Bezos, when the former invited Bezos to tour SpaceX in 2004.

After the tour, Musk sent a "curt" email to Bezos about his annoyance over not having been reciprocally invited to see Blue Origin's factory, per Isaacson.

A surprised Bezos then responded to the email with an invite.

After touring Blue Origin, the pair had dinner together with their then-wives, MacKenzie Scott and Justine Musk, per the biography.

According to this book and another account of the meal — Christian Davenport's book, "The Space Barons" — the dinner did not go over well because Musk gave seemingly unwanted advice to Bezos. It is not clear what the advice was.

In the 18 years since that dinner, the two have sparred over their respective space ambitions, made public digs at each other, and traded places as the world's richest person.

Jeff Bezos is currently the world's third-wealthiest person, with a net worth of $165 billion — largely owing to his stake in e-commerce giant Amazon — per the Bloomberg Billionaires Index. Meanwhile, Musk currently takes the top spot on the list, with a net worth of $242 billion.

After that dinner, their relationship again entered the public eye after a dispute over the use of a NASA launchpad in 2013, which SpaceX eventually won.

The two have taken public swipes at each other since, with Bezos congratulating Musk on SpaceX landing its Falcon 9 spacecraft in 2015 — a similar feat was already achieved by Blue Origin — and Musk referring to Bezos as "Jeff who?" in a BBC interview.

The feud again reignited in 2021 when NASA awarded SpaceX a $2.9 billion contract to send humans to the moon, which Blue Origin unsuccessfully appealed. This dispute gave rise to Musk mocking Bezos by tweeting, "Can't get it up (to orbit) lol."

"He should spend more time at Blue Origin and less time in the hot tub," Musk later said about their space race in an interview with the Financial Times in 2021, "In some ways, I'm trying to goad him into spending more time at Blue Origin so they make more progress."

Musk and Bezos did not immediately respond to requests for comment from Insider, sent outside regular business hours.