Italy's top criminal court has ruled there is `'abundantly" clear evidence that a stray missile caused an Italian passenger jet to crash into the Mediterranean Sea in 1980, killing all 81 people aboard.

Quoting from the Rome ruling on Monday, the Italian news agency LaPresse said the court upheld a Palermo appeals ruling that Italian radar systems didn't adequately protect the skies and Italy must compensate the victims' families.

What caused the Itavia DC-9 to crash during a flight from Bologna to Palermo has been one of Italy's enduring mysteries.

Some theorized a bomb exploded. Others contended the jet was caught in the crossfire of a military aerial dogfight, with a Libyan plane possibly the target. French, U.S. and NATO officials have denied military activity in the skies that night.