Two former air force generals were definitively acquitted on Wednesday on charges that they failed to tell the truth about a mysterious 1980 airplane crash in which 81 people perished.
The Supreme Court confirmed the ruling of a lower appeals court which found Lamberto Bartolucci and Franco Ferri not guilty in 2005.
The two generals, who are both in their 80s, had been accused of failing to inform political authorities of the presence above the southern Italian island of Ustica of other aircraft when a civilian airliner went into the sea on June 27, 1980.
The generals have always maintained their innocence.
The Supreme Court's ruling will prevent the families of the crash victims obtaining compensation.
State lawyers had been seeking the court's correction of the wording of the lower court's 2005 ruling, a technicality which would have allowed the compensation claims.
But the Supreme Court rejected their case.
Ferri said after the verdict that "this is the end of a nightmare. Finally my honesty has been definitively recognised".
Lawyers representing the victims' families, however, expressed anger and bitterness.
"One of the greatest Italian tragedies will now remain a mystery. I feel great bitterness and indignation. No-one has been made to pay after 27 years," they said.
Dossiers, books, and even a film called The Rubber Wall have been produced over the years about the mystery-shrouded summer night when the domestic airliner, belonging to the now-defunct Itavia line, crashed into the sea on its way from Bologna to Palermo.
Two international panels examined the wreckage. One concluded the plane had been hit by a missile, while another thought a bomb had been planted aboard the craft - another terrorist act similar to that carried out with even greater loss of life at Bologna train station later that summer.
But investigating magistrate Rosario Priore and the prosecutors who have succeeded him insisted they had found clear evidence of flight tracks being tampered with and radar scans cleaned up to remove all trace of other planes in the vicinity of the Itavia jet.
Priore and victims' relatives think the plane may have become caught in a dogfight between Nato planes and a Libyan jet whose wreckage was found in the southern Italian highlands some months after the Ustica crash.
Italy has repeatedly asked NATO, and in particular the United States and France, for full cooperation in clearing up the incident.
According to reconstructions of the event contained in fictitious accounts, the Libyan jet, perhaps escorting Colonel Gheddafi, hid under the Itavia jet and a NATO missile hit the wrong target.
Whatever the truth of the matter, it is unlikely to emerge in the courtroom but may only come out when NATO records are declassified in years to come, many of the theorists say.
Italy's many conspiracy theorists have also pointed to a suspiciously high mortality rate among air force staff and other people linked to the case, with four committing suicide by hanging.
Another died of a heart attack at the age of 37.
Among the witnesses who gave evidence since the trial started on September 28, 2000 were former premier and now interior minister Giuliano Amato and former Italian president Francesco Cossiga.
Cossiga argued strongly that a technical fault caused the crash.
