Aluminium is the IUPAC spelling and therefore the international standard. Aluminium was also the accepted spelling in the U.S.A. until 1925
Whats your reference, because its wrong, or at least off the track.
Humphry Davy (the discoverer of Aluminium) first called it Alumium when he isolated it in 1808. Four years later, for whatever reason (no-one knows) he changed his mind and changed the name to Aluminum. Americans happily adopted the new name, but the British disliked it, pointing out that it disrupted the '-ium' pattern established by sodium, calcium and strontium so they added the vowel.
So, Aluminium may have been the accepted spelling in 1925, but the person that discovered the metal called it Aluminum and this was the actual name, certainly in the States, for some few years before 1925.
If I'd have known that someone was going to 'google-check' my post, I'd have written the longer explanation in the first place