The cause of the destruction Thursday of a Siberian Airlines passenger jet with 78 people aboard remains shrouded in uncertainty, with Russian investigators conceding at least three possible explanations for the mid-air explosion: a terrorist attack, a mechanical catastrophe, or the accidental launch of a surface-to-air missile from Ukraine.

The plane was carrying Israeli passengers, mainly immigrants from Russia, from Ben Gurion Airport in Tel Aviv to the Siberian city of Novosibirsk, where they were to visit relatives for the festival of Sukkot. Dozens of relatives have begun flying from Siberia and Israel to the Black Sea port of Sochi, where recovered bodies are being brought for identification.

The plane exploded at 36,000 feet as it was crossing the Black Sea from Turkey to Russia. It was about 115 miles south of the Crimean peninsula, the southernmost point of Ukraine, where Ukrainian and Russian military forces were conducting a joint exercise that involved the firing of dozens of surface-to-air missiles.

The US government was the source of initial reports that Siberian Airlines Flight 1812 had been hit by a Ukrainian missile. US intelligence officials told the Washington Post that the missile launch had been detected by the US National Security Agency, which conducts satellite reconnaissance of such weapons firings throughout the globe. The launch took place only minutes before the destruction of the plane, the Post reported.

All of the governments involved are dealing with the tragedy, not from the standpoint of the interests of the families of the victims, but with an eye to their diplomatic and military concerns in a region that is rapidly becoming a staging area for US military intervention. (US military transports were flying 1,000 special operations troops into Uzbekistan at the same time that the Siberan jet was shot down.)

Ukraine initially rejected outright the claim that one of its missiles could have destroyed the passenger jet, declaring that the flight was far outside the range of the missile and that ground radar had seen no planes passing through the area of the war games. One Ukrainian military spokesman also claimed that the military exercise had not even begun until an hour and a half after the explosion.

The Ukrainian Defense Minister, Oleksandr Kuzmuk, insisted it was impossible for the airliner to have been shot down as all the rockets used during the training exercise had self-destruct mechanisms in case they deviated from their course.

“The direction of the firing and the distance do not correspond to the plane’s explosion site, either in theory or in practice,” said a Ukrainian Defense Ministry spokesman. “All the hits by the rockets used during the exercise were recorded by corresponding devices and reached their targets.”

The Ukrainian daily newspaper Den criticized the US and European press coverage, writing, “As soon as news of the Russian Tu-154 plane crash broke yesterday, some Russian and Western media rushed to blame the Ukrainian armed forces. This was done in complete absence of any official information.”

But under intense pressure after the US declaration, Ukraine Prime Minister Kinakh said that the missile theory had “a right to exist,” while pleading that it was too early to draw conclusions before any investigation.

Russian officials initially sought to blame the plane explosion on unnamed terrorists. The sections of the plane recovered from the Black Sea include the cockpit, nearly intact, which reportedly had a series of punctures in the metal that resembled bullet-holes. Forensic experts are now examining this evidence.

Russian President Vladimir Putin has embraced the US war drive against Afghanistan and sought to link the US campaign against Osama bin Laden with the ongoing Russian war against Islamic guerrillas in Chechnya. The official Russian probe of the air disaster, which destroyed a Russian plane and Russian crew, began with the chief investigator invoking the country’s anti-terror law.

But in the face of US insistence on the missile theory, Putin reversed himself, effectively endorsing the American view, although Russian military personnel were participating in the war games in Crimea, monitored the missile launches and reported no unusual outcomes.

The American response to the tragedy has been peculiar in the extreme. Within a few hours of the explosion, even before any fragments of the plane had been recovered, let alone the black boxes that would provide more substantial evidence, the US government declared the destruction of 78 lives to be a regrettable accident and not a terrorist attack.

US officials were remarkably free in citing the information supplied by US satellites using infrared detectors, usually a closely guarded secret. The New York Times noted, “the United States vigilantly monitors missile launches around the world, and has long kept a hawk’s eye on the Black Sea from cold-war-era observation posts in Turkey.”

The response of the American media, especially the television networks, was notably muted, without the sensationalism that usually attends their coverage of such tragic events. One should contrast this treatment with the coverage of the TWA Flight 800 disaster, which the media immediately declared to be the result of a terrorist bomb. This theory persisted for nearly two years, until the FBI was compelled to admit that a defect in the center fuel tank of the Boeing 747 jet was the likely cause of the explosion.

The rapid US intervention to “solve” the mystery of the mid-air explosion and the relative indifference of the media have a political explanation. The disaster takes place at a time of maximum tension between the Bush administration and the Israeli government, only two days after the State Department revealed that the US government was prepared to sanction the establishment of a Palestinian state, and only hours after Sharon denounced Washington in the most strident terms, comparing its policy toward the Arab regimes in the Middle East to the Munich appeasement of Hitler.

The Bush administration wanted to make sure that the Israeli government could not use the Siberian Airlines disaster as a means of provoking further conflicts with the Arab states over alleged terrorism, and perhaps disrupting the fragile coalition backing a US attack against Afghanistan.

In Israel there were hints that the crash itself might have been a product of the growing tensions in the region. The Jerusalem Post published a commentary on the crash under the extraordinary headline, “Sharon’s warning shot.” The text of the editorial did not substantiate the suggestion that the shooting down of the airliner was a warning to the Israeli government. Instead, it linked the crash to Sharon’s earlier speech comparing Bush to Neville Chamberlain.

But in worried tones, the newspaper advised: “It is imperative that there be complete cooperation among Ukraine, Russia, and Israel, and any foreign intelligence agencies that can shed light on what happened. The sooner the cause of the crash can be positively determined, the better it will be for relations between the nations involved, and at least the added burden of uncertainty will be lifted.”