It is still unclear what caused the Russian Tu154 plane to crash yesterday.

At present a government commission of investigation into the crash is working in Sochi, headed by Secretary of Russia’s Security Council Vladimir Rushaylo. The first meeting of the commission took place at the airport last night, upon its arrival in Sochi. This was a closed meeting, and the press was not admitted.

Some foreign media sources reported yesterday that the Russian plane might have been brought down accidentally by a surface-to-air missile fired during a Ukrainian military exercise in Crimea.

In the past there have been some incidents when armed forces brought down civilian aircraft. In 1988 the American missile cruiser Vincennes, while patrolling waters of the Persian Gulf, accidentally shot down a Boeing 727 passenger plane of an Iranian air company. The aircraft was following an international air route marked on all maps. As a result, 263 people were killed.

The Ukrainian Defense Ministry denied any involvement. The Defense Ministry press service reported that yesterday Ukrainian air defense forces had been engaged in military exercises in the area, near the Opuk cape, and missiles had been fired during the exercises. According to media reports, the Tu154 plane crashed into the Black Sea 180 km off the Russian coastal town of Adler at 13:44 Moscow time. It was a regular charter flight of the Russian Sibir airline company en route from Tel Aviv to the Siberian city of Novosibirsk.

According to the Ukrainian Foreign Ministry press service, immediately after the catastrophe Ukraine’s radio locator reconnaissance forces checked the area of the military training exercises and nearby regions and established that no aircraft had entered the zone of exercises. The range of the missiles did not overlap with the route of the aircraft and the site of the crash.

The press service said the entire area of the military training exercises, including within the range of the missiles, had been blocked well ahead of time. Air traffic controllers of airline companies operating flights near the area of the training exercises had been warned of missile launches. All rockets used in the military exercises had guaranteed service lives and self-destruct mechanisms in case they deviated from course.

The missiles were fired within a range of 30 km to 35 km. All rockets fired were monitored by control mechanisms: all of them hit their targets within the exercise area.

Thus, the theory that the plane had been downed by Ukrainian forces should be rejected. Now the main theory of the accident is a terrorist act.

Reportedly, there had been an on-board explosion in mid-air before the plane fell into the ocean. A pilot of an Armenian plane An24 flying in the area said he had seen a passenger plane exploding in the air and breaking as it fell into the sea.

In spite of the fact that Israel operates some of the most stringent aviation safety measures, there is a possibility that an explosive device might have been planted on the plane at the airport.

The crash of the Tu154 killed 66 passengers and 12 crew on board.