Angelo Lonardo was the highest ranking mafia member ever to flip at that time. In all fairness, he was railroaded by a few of his underlings who were dealing major narcotics behind his back. Just like in the movie Goodfellas when Paulie tells Henry how his friend Griggs got 20 years for saying hello to a guy selling junk behind his back.

Here are a few articles on Big Ange:

1. http://www.onewal.com/maf-invl.html (Lonardo Testimony 1988)
2. http://www.americanmafia.com/Feature_Articles_343.html