The suggestion that the crash, in which 75 people, including four Britons, died, happened after one of the pilots allowed his 15-year-old son into the cockpit was made at the weekend by several newspapers, including the Moscow Times.
French and US experts who were reporting to the official Russian commission of inquiry have said that their analysis of the black box shows that there was nothing wrong with the nearly new plane, but that there was a voice on the tape which did not belong to any of the pilots.
Valery Eksuzian, the general director of RAL, the international offshoot of the old Soviet airline Aeroflot, which now confines its activities to domestic operations, cautioned against drawing hasty conclusions.
The microphones in the cockpit were very sensitive, he said, and if the pilots' door had been open, they could have picked up a voice at the front of the plane, perhaps that of a steward.
'If there was a stranger in the pilot's seat, and this must be proved, then his incautious actions could not lead to a tragic outcome. The aircraft's automatic-control system can restore the initial dimensions of a route. In addition, the co-pilot can correct any mistake of the pilot at any moment,' Mr Eksuzian said. The military experts, if they were brought in, would use special equipment to play the tape more slowly.
The plane, which RAL had leased from the West European consortium Airbus Industrie, was on a flight from Moscow to Hong Kong. Without warning it plunged to earth from its cruising altitude, something which planes almost never do unless there has been a mid-air collision or a bomb explosion. The Russian pilots, who were buried after a funeral service at Moscow's Sheremetyevo Airport last week, were described as experienced fliers.
Mr Eksuzian said that after the plane 'started to act in ways which were not programmed into the autopilot', the crew expressed astonishment, which was recorded on the tape.
RAL must be very concerned about the reports of the teenager which, if true, would seriously damage the reputation of a young airline. It is not beyond the bounds of possibility that a passenger was allowed into the cockpit. On internal Aeroflot flights, because of overcrowding, passengers are sometimes put with the pilot.
I have flown from Tbilisi to Moscow sitting in the navigator's seat. The ill-fated Airbus was not, however, overloaded but flying at only half capacity. Several relatives of the pilots were registered as passengers on the flight.