It's unlikely space race billionaires Elon Musk and Jeff Bezos are going to be sharing a rocket to the moon any time soon, with their war of words continuing to escalate.
Amazon, founded by Bezos, wrote to the Federal Communications Commission (FCC) at the end of August to protest at Musk's SpaceX company's plans to extend its Starlink satellite broadband service.
SpaceX replied that Amazon's move was just an obstructionist tactic because its technology wasn't ready.
Musk followed that up with a tweet, saying "Filing legal actions against SpaceX is *actually* his full-time job."
Now the latest back and forth has become much more personal with the letter, signed by Lead Counsel C Andrew Keisner, attacking Tesla CEO Musk directly.
"Whether it is launching satellites with unlicensed antennas, launching rockets without approval, building an unapproved launch tower, or re-opening a factory in violation of a shelter-in-place order, the conduct of SpaceX and other Musk-led companies makes their view plain: rules are for other people, and those who insist upon or even simply request compliance are deserving of derision and ad hominem attacks," it said.
The letter continued, highlighting times South African-born Musk has publicly attacked those who opposed him, including daring the county of Fremont, California to arrest him for re-opening a Tesla factory in defiance of a shelter-in-place order during the start of the COVID-19 pandemic.
It concluded with a warning: "If SpaceX and Musk continue to hold themselves above the rules, they should buckle up: they will only draw further protest from Amazon and others who want to see rules applied to everyone equally".
"Musk and SpaceX will likely continue to respond as they have here, and the chaotic and resource draining cycle will continue. Amazon asks that the Commission show SpaceX that the rules apply to it as well. This - and only this - will free all those involved to return to the real work of closing the digital divide."
The letter's release comes just a day after the Tesla CEO responded to a tweet reporting Bezos had reportedly invested in an anti-aging startup researching how cells age and how to reverse it with "And if it doesn’t work, he’s gonna sue death!".
This is just the latest in a long battle between the billionaires. Bezos's Blue Origin company has already sued to overturn a decision by NASA to award SpaceX a sole contract to build a lunar lander.
Blue Origin had previously offered a US$2 billion discount to the space agency to help change its decision to award the multi-billion dollar deal to SpaceX.
With that offer declined, the decision will now be left to the court. Meanwhile the lander programme has been halted until at least November 1, causing further delays for NASA's plans to get back to the moon by 2024.