A week and a half ago, the San Francisco 49ers Week 12 home matchup with the Arizona Cardinals was preceded by an amusing banner flying over Levi's Stadium. A GoFundMe was set up to finance a banner suggesting Jed York and the 49ers should "mutually part ways". It did not last for very long due to the cost of flying it around, but it got local media attention.
It turns out the folks at Levi's Stadium took notice of it. Ryan Sakamoto of NinerFans.com was able to put together this video with audio between California Highway Patrol and the air traffic control tower at the nearby airport. CHP said the following, "Levi's security is requesting that one of the two banners appears to be not permitted, and not advertising something that they wanted them to be advertising."
The pilot of the plane chimed in and said this was a free speech issue. The control tower then said CHP should have Levi's security contact them directly.
Ryan got a comment from the 49ers stating it was a standard procedure when an unidentified airplane is around the stadium's air space. His article also includes a look at NFL policy regarding flying planes over games.
I would like to have been there to hear the discussion that led to Levi's security making the call to CHP. It is entirely possible the 49ers saw this and were sufficiently annoyed that they called to have it taken down. I am skeptical the message had absolutely nothing to do with the decision to make the call, but I wasn't there, so who knows.
There are plans for another banner against the Cincinnati Bengals. Some have suggested doing the same thing during the Super Bowl at Levi's Stadium, but there is no way that will legally happen. Someone might try, but aside from a potential pre-game military flyover, it will be a no-fly zone over and around the stadium.