The single-engine Pilatus PC-12 had taken off from Milan’s Linate airport shortly after 1pm headed for Olbia in the north of the Italian island of Sardinia.
It crashed just a few minutes later into a building in San Donato Milanese, a town southeast of Milan, according to aviation agency ANSV, which has opened an investigation.
Witnesses said the plane was already in flames before it crashed into an office building undergoing renovations.
Petrescu’s 65-year-old wife, who also had French nationality, and their son Dan Stefano, 30, were killed.
Italian media identified the other passengers as entrepreneur Filippo Nascimbene, a 33-year-old from Lombardy, with his wife, young son and mother-in-law, who have French nationality.
Petrescu, 68, was one of Romania’s richest men. He headed a major construction firm and owned a string of hypermarkets and malls. He also held Germany nationality, the Corriere della Sera newspaper reported.
Flames engulfed the two-storey building, next to the yellow line subway terminus.
“The impact was devastating,” Carlo Cardinali, of the Milan fire brigade, told news agency Ansa.
Deputy prosecutor Tiziana Siciliano was quoted by Corriere as saying that the plane’s black box had been recovered.