A few hours later, wreckage from the DC-9 was spotted in the Tyrhennian Sea off the island of Ustica, near Sicily. There were no survivors.

The cause of the tragedy remains one of the Italy's most enduring mysteries and there was a painful reminder recently that the case has still to be resolved when the stricken plane made its final journey back home to Bologna.

For years it has been languishing in an aircraft hangar in Rome having been put back together by air accident investigators, while various panels and commissions tried to find the truth about the crash.

Its 11-hour journey across central Italy was an eerie sight. The nose of the commercial airliner was on the lead lorry, enclosed in a plastic wrapping like a transparent shroud, followed by sections of the fuselage, both wings and finally the tail. "It looked like a wounded bird," noted La Repubblica.

The wreckage was received by families of the victims, still mourning the loss of their loved ones. Elena de Domincis, whose sister Rosa was a stewardess aboard the fated flight, touched the fuselage as if it was a sacred relic and said:" Finally, I have a place where I can imagine Rosa ... before there was only the sea." The plane is to go on display next year in Bologna's Museum of Memory.

When the passenger jet crashed, the immediate theory was that it was a tragic accident caused by some kind of mechanical or structural failure.

Then there was the suggestion that terrorists could have planted a bomb, although that theory was rejected, and in 1999 an exhaustive investigation by Judge Rosario Priore, one of Italy's most respected legal figures and an expert on terrorism cases, gave the definitive version of what happened. He concluded that the plane had probably been caught in a dogfight between NATO jetfighters and Libyan MiGs.

Radar evidence showed that there had been intense military activity in the area on the night Flight 870 was heading innocently towards Palermo, including the presence of US, French and Libyan military aircraft and an aircraft carrier that, according to some reports, was British.

The investigating magistrate said he believed there had been a plot to shoot down a plane carrying Libya's Colonel Muammar Gadafy and that the commercial airliner had been unwittingly caught up in the "war-like scenario". He said the passenger jet had either been brought down by a missile or had plunged into the sea after swerving to avoid a mid-air collision with one of the jetfighters.

In his 5,488 page report, Mr Priore said he could not say for sure who had caused the deaths of the 81 people on board but he said that his investigation and previous investigations into the tragedy had been deliberately obstructed by the Italian military and members of the secret service, who had complied with requests from NATO to cover up the tragedy.

Four Italian air force generals and five other people were indicted, charged with high treason and perjury. They denied all the charges and although the case went ahead, it collapsed because of time restraints and insufficient evidence.

There is now a glimmer of hope that there will be a new inquiry and that those responsible may yet be brought to justice. Italian senator Walter Vitali has called on the countries involved - the US, France, Britain and Libya - to collaborate with any future investigation in Italy and to reveal once and for all what happened on the night of June 27, 1980.

"We still hope the truth will come out," said Daria Bonfietti, who lost her brother in the crash and who is chair of an association of relatives of the victims. She told Guardian Unlimited: "We know that very probably the plane was struck down by a missile. Too many people have been keeping this secret for too long but we will not give up until we know everything that happened."

She said she hoped the newly elected government of Italian prime minister Romano Prodi would press for an explanation "from the allies that are involved because they have never answered our requests for information".

Italy's president, Giorgio Napolitano, has also given his support to a new inquiry. "Time is no obstacle in the search for truth," he said.