Ricky explained the basic stuff but still there are some details which cannot be ignored...

In 1970 when Cerone (Elmwood Park and W Grand Av) and Phil Alderisio (Melrose Park, Lake View and Grand Av) went to jail, that same year Aiuppa (Melrose Park and Cicero) and Nicoletti (Melrose Park, Lake View and Grand Av) had more than several meetings with Ricca and Accardo, probably rgerading the subject on who was going to take over the Outfit, since the prebious boss Cerone was in prison, and on top of that during this same time period, the previous underboss Fiore Buccieri was was supposed to take over the throne, got sick of cancer. So in 1971 the path was clear for aiuppa to take the so-called acting boss position, while Nicoletti took the number two spot, with Accardo and Alex at the top.

In 1973 I think Cerone was out of jail and according to Alex, he asked Accardo if his position as an adviser can be replaced by Cerone since he was already out of jail, and Alex had to take a step back since his wife was ill. This means that Cerone took the advisory role until Alex's return, and one of Cerone's active roles during this period were his numerous meetings with Giancana and Spilotro in 1974. When Alex returned to the scene in 1975, Nicoletti was allegedly shelved and so Cerone allegedly again took the number two spot. Also dont forget that Cerone and Aiuppa previously didnt respected each other so much but still Cerone was a previous boss and so I presonally, together with other several researchers, think that from 1976 until 1983, Aiuppa and Cerone functioned on the same level, besides one being the number two guy or the top guy.

One thing clarifies that during that same period Aiuppa officially held the number one spot since we have one info that he presided over a ceremony during the early 80s but again we believe that in the eyes of some lower level members at the time he and Cerone were almost equal.