UFO - Unidentified Flying Objects

Seeking for objects that are "on the air" but are not designed for that scope; for instance, a book coming out of a window while still flying (some one is having a big discussion...?). Be careful: objects with wings are NOT allowed, as well as any kind of animal or human being (at least as the main subject). The object(s) is to be clearly separated from any link to the ground or to people (otherwise the definition of "flying" would have no sense...), so for instance kites are NOT allowed.