On 27 October 1954, players and spectators at Florence's Stadio Artemio Franchi began looking upward during a match between Fiorentina and Pistoiese.

This case matters because it is a documented mass event whose object identity remains unresolved.
Documented
On 27 October 1954, players and spectators at Florence's Stadio Artemio Franchi began looking upward during a match between Fiorentina and Pistoiese.
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.
Secondary / debated material.
Documented source.