The Russian airline Kogalymavia blamed "external activity" for its plane crash on Saturday in Egypt's Sinai peninsula in which all 224 people on board were killed.
"The only reasonable explanation is that the plane crash was due to external activity," the BBC quoted an airline official as saying.
An investigation by aviation experts using data from the aircraft's "black boxes" has yet to give its conclusions.
A Kremlin spokesman said terrorism could not be ruled out as a possible cause of the crash whose responsibility was taken by a group affiliated by the IS.
At a news conference in Moscow, the deputy director of the airline, which was renamed as Metrojet, ruled out a technical fault and pilot error.
"The only explanation for the plane to have been destroyed in mid-air can be specific impact, purely mechanical, physical influence on the aircraft," Alexander Smirnov said.
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"There is no such combination of failures of systems which could have led to the plane disintegrating in the air," he added.
Another airline official acknowledged that there had been previous damage to the plane's tail in 2001 during take-off.
But he said that the damage had been repaired, and was not thought to be a factor in the crash.
The plane lost speed and started descending rapidly, and the crew made no attempt to contact and report about the situation on board, Smirnov added.
Saturday's disaster happened shortly after the Airbus 321 took off from the Egyptian resort of Sharm el-Sheikh.