Finmeccanica's former chief Giuseppe Orsi and the former head of the AgustaWestland subsidiary, Bruno Spagnolini, had both originally been sentenced to two years in prison in October 2014 following an investigation into the sale of 12 luxury helicopters to India's government.
Their sentences were subsequently extended to four-and-a-half years and four years respectively when the case went to appeal in April 2016. But in December 2016, Italy's highest court annulled the sentences, arguing that the previous two rulings had differed too greatly.
Milan's third court of appeal on Monday upheld that decision, saying that the facts of the case had not been sufficiently proven.
Orsi was arrested in 2014 and resigned as chief executive of the aerospace group a short while later.
India cancelled the deal with AgustaWestland in January 2014 amid allegations that the company paid bribes to win the 556-million-euro ($662 million) contract
The aborted deal was a severe setback for Finmeccanica, having already been hammered by the global financial crisis.