The event is meant to mimic the ending sequence of the anime series, in which a flock of flying pantsu is seen soaring in formation. Called Sora Fes!, the event will feature ornithopters (airplanes with flying wings) shaped like pantsu.
Tickets to event are around $11, and for twice the price an attendee may return home with one such ornithopter. Also available at the event will be a workshop on constructing ornithopters.
To see the ending sequence referred to, click here: (Sora no Otoshimono).