httpv://www.youtube.com/watch?v=s6v3p9l3mP4
From YouTube:
4-16-2012 – Military conducts Urban Warfare Training over the skies of Downtown Chicago with Blackhawks A/MH-6 Little Bird helicopters and Heavily Armed Special forces. Residents reported seeing these teams for hours as they made their way through downtown Chicago’s skyscrapers. More info @ http://offgridsurvival.com/urbanwarfaredrillsdowntownchicago/
