No one seems very well-informed about this, and I saw it happen in real time; so I'll tell you what I know.
The guy who conceived this is a Miami Dolphins fan. He's much like you and me; although I suspect he's more like me than most of you, judging by your posts. He's a good fan who loves this team. He's passionate; he's ALL about the Dolphins. But he's been frustrated for the last few years by the direction of the team he loves.
He's been frustrated by being ahead of the curve; by seeing what it has taken others until now to see, when all the damage is done. Frustrated by being vilified by people who are supposed to be his fellow fans—brothers for knowing far longer than most that this franchise was in serious trouble, and that the cause was a GM who couldn't find any NFL star-caliber players other than on the defensive line.
Although we fans pay 100% of the revenues of these NFL teams, we are powerless in terms of affecting anything at all with regard to how our beloved team is run. So this guy did something; the one thing fans can still do: express an opinion. He arranged to do it in a very public way.
As to the details; the cost of displaying the banner was $985. It's important to note that 20+ people donated to this.
But here's the most interesting part: from the moment when this guy conceived the idea, to when he opened the donation account, to the last donation and contracting the plane company, little more than 45 minutes elapsed. That's right—it took just over 20 people about a half hour to donate enough to get this thing in the air. Twenty of your fellow fans.
If that doesn't tell you something about the general frustration of the fanbase and their willingness to put their money where their mouths are, then nothing will.