It's not too unusual to see various flying banners with messages of support for one side or the other on the day of a championship game. In fact, one just flew over the MLS Cup Final being played between the LA Galaxy and New England Revolution in LA. Let's see what it says...
That banner is advocating bringing promotion and relegation to US soccer, something that MLS, the nation's top league by far, has always been reticent to even consider partaking in. Even with the league expanding rapidly, aimed at 24 clubs by the end of the decade, there's been no sign that MLS is even thinking about adding pro/rel any time soon.
That hasn't stopped an aggressively vocal minority from making lots of noise in support of pro/rel on Twitter and other social media platforms. Some have even been known to inject their topic of passion in to MLS-related conversations that have nothing to do with promotion and relegation across multiple divisions. With those charming folks in mind, seeing a banner like this flying over MLS' biggest event of the year may not be surprising, but it's certainly amusing.