ROME -- Itavia Flight 870 was entering the final leg of a routine domestic trip from Bologna, Italy, to Palermo, Sicily, one clear summer evening when it suddenly plunged into the Tyrrhenian Sea near the small island of Ustica, killing all 81 people aboard.
Mechanical failure was ruled out early on, and almost 33 years later, the causes that led to the crash on June 27, 1980, are still a topic of passionate debate in Italy, fueled by three decades of inquiry boards, parliamentary commissions, countless expert reports and one of the longest judicial inquiries in recent Italian history. But despite all that, no formal charges have ever been filed in connection with the crash.
The crash, known as the Ustica affair, has produced legions of conspiracy theories here, the way the Kennedy assassination -- or, on a lesser scale, the crash of TWA Flight 800 off Long Island in 1996 -- have in the United States. But in the Ustica affair, the case for a cover-up is far stronger.
Last week, when Italy's highest court ruled that the country's Defense and Transportation Ministries had to compensate the families of some of the victims, the court implicitly acknowledged the most widely accepted theory behind the crash: that a missile fired by a warplane had hit the twin-engine McDonnell Douglas DC-9 on Itavia, a now-defunct domestic Italian airline. But the court did not say where that missile came from.
To conspiracy buffs, it was vindication -- to a point.
"It's like the O. J. Simpson affair, where he got off in criminal court but was found guilty in a civil procedure and had to pay damages," said Andrea Purgatori, an investigative reporter whose exhaustive book on the disaster and the presumed cover-up was made into a 1992 film.
Over the years, several Air Force officials have been investigated for withholding evidence -- wiping clean flight tracks and radar scans -- and four generals were tried on charges of treason and obstructing investigations. But no one has been convicted.
In this hothouse atmosphere, it is not surprising that conspiracy theories have proliferated over the years. The crash has been blamed on U.F.O.'s (several Web sites subscribe to this reconstruction) or domestic terrorism (the Bologna train station was bombed not five weeks later, killing 85 and wounding dozens more). In this scenario, the plane went down after a bomb exploded onboard, most likely in the toilet.
The missile theory gained a new impetus in 2008 when Francesco Cossiga, the prime minister at the time of the Ustica affair, said in an interview that the flight had been shot down by French military planes. Mr. Cossiga did not provide further details, nor can he. He died in 2010, at age 82.
Cover-up theories have been fueled through the years by what news reports have described as a "suspiciously high mortality" among military personnel and others connected to the case. (Mr. Cossiga is not included among them.)
Through traffic accidents, shooting deaths and suicides by hanging, there were 36 untimely deaths by 2011, according to a television report about Ustica. The program also cited a number of "bizarre accidents" that befell Ustica witnesses, like being run over by a tricycle and slipping on a banana peel in a Rome subway station.
"What terrifying truth warranted a cover-up at the cost of the lives of all these people?" asked the show's host, Adam Kadmon, who plays a mysterious masked vigilante who investigates topics like Ustica, underskin microchip implants and, more recently, Michael Jackson's prophecy about Sept. 11, and favors the French missile theory.
At the time, proponents say, Italy was covertly allowing Libyan aircraft to fly through its airspace undisturbed. They did so by gliding in the slipstream of Italian domestic aircraft, where they could not be detected by radar. On the night of June 27, 1980, there were unsubstantiated reports that Col. Muammar el-Qaddafi was on one of those planes, the theory goes, and French forces tried to shoot it down to kill the Libyan leader, but hit the DC-9 by mistake. Don't ask why. It has to do with rebels in North Africa and jockeying for oil concessions between Italy and France.
But Colonel Qaddafi had been warned of the plan and never boarded his plane, according to this reconstruction, which also says the pilot made a successful emergency landing at sea. There, a British submarine reached it and deployed scuba divers to plant explosives to sink the plane and to silence potential witnesses to the assassination attempt.
One hypothesis, detailed by an investigative journalist, Claudio Gatti, holds that the plane was shot down by Israeli forces that mistook it for a plane carrying enriched uranium earmarked for Iraq. "No country would attack in the Mediterranean for anything but extraordinary reasons," and Israel "had that reason," Mr. Gatti said. "It's the only scenario that makes sense."
The Western warplane scenario has gathered weight through the years, as Italian prosecutors disclosed that several NATO planes were flying in the same airspace that night.
But the dynamics of the grisly accident are still hypothetical. Was there a near collision with the DC-9? Was there a dogfight between NATO aircraft and Libyan jets (a theory substantiated, for some, by the recovery three weeks later of the wreckage of a Libyan MIG fighter in the remote Calabrian countryside)? Was the missile fired from a launcher based on land or sea, specifically from the French aircraft carrier Clemenceau or the United States aircraft carrier Saratoga? (The United States military denies any involvement.)
"We've known since the judicial inquiry issued in 1999 that a missile was involved, but the perpetrators are still missing. We don't know which country shot it," said Daria Bonfietti, who heads the association of families of the victims that has relentlessly spurred the justice system to pursue the case. The truth lies under an elaborate cover-up, she said, one in which "everyone has something to lose."
Prosecutors in Rome are still pursuing the Ustica affair. Several international rogatorie -- legal requests for information -- have since been sent to Belgium, France, Germany and the United States, but responses have been slow in coming, leading the victims' families to accuse those countries of dragging their feet.
Prosecutors say there are no time limits to such requests, which "depend solely on the collaboration that countries see fit to give," said Erminio Amelio, one of the prosecutors currently leading the criminal investigation, which has passed through various hands over three decades.
Even though much has changed since that night in the Mediterranean almost 33 years ago -- like, for instance, the end of the cold war -- official sensitivities are still high, and no one expects any of the governments thought to be involved to come clean anytime soon.
"This is an incredible story, where a series of colossal lies have been told," Mr. Purgatori, the investigative reporter, said.
This article originally appeared in The New York Times.