Here is a video from TED-Ed that explains why. TLDR: phones looking for a signal broadcast on high power, but planes move so fast that you can end up right next to a cell tower so the high power signal can interfere with other phones trying to communicate.
I disagree with how he phrases a few things, but I think it's mostly accurate.
The first Star Trek game I played was a shareware version of EGA Trek for DOS, which was also one of the first computer games I ever played.
I remember it would tell you a starbase was under attack and you would have to go there to defend it. One of my torpedoes missed and hit a star which made it go supernova, destroying the enemy ship. Fun times.
It is because they classified Musk as a Special Government Employee, which can only be employed for 130 days out of the year. The article references the 130 days, but doesn't say anything more about it.
https://www.doi.gov/ethics/special-government-employees