Being that Red Bull is now a behemoth of a company and can no longer get away with impromptu, illegal stunts, I would have to assume they had all the proper permits and whatnot for this spectacle. But I also have to imagine that this scared the crap out of some the unsuspecting spectators on the ground.
From Red Bull:
On November 3rd, at approximately 6:25pm in Chicago, Illinois, locals reported a mysterious fireball falling from the Chicago skyline. What was this fireball, you ask? The beginning of an apocalypse? Maybe a meteor? Well, Jon Devore, Mike Swanson and Sean MacCormac from the Red Bull Air Force took an epic wingsuit flight in the darkness of night, blasting flares as they fell down from the sky before they landed safely on the Lake Michigan Shoreline to kick off Red Bull Art of Can.
Source: Red Bull