During April 2013, several employees at the Collahuasi copper-mining complex in northern Chile observed a bright object in clear daylight.

This case matters because it is a documented physical event whose object identity remains unresolved.
Documented
During April 2013, several employees at the Collahuasi copper-mining complex in northern Chile observed a bright object in clear daylight.
Debated
The identity of the object
Debated
The adequacy of the conventional explanation
Unverified
Extraterrestrial origin
Unverified
Any claim stronger than the record supports
Sources are kept in separate layers: official and contemporary material is documented; secondary UFO literature is treated as debated, not as primary evidence.
Documented source.