The Russian airline Kogalymavia has blamed “external influence” for Saturday’s Sinai plane crash which killed 224 people.
A senior airline official said: “The only reasonable explanation is that it was [due to] external influence.”
An investigation by aviation experts using data from the aircraft’s “black boxes” has yet to give its conclusions.
The head of Russia’s Federal Aviation Agency said it was premature to speculate on the cause of the crash.
“This kind of talk is… not based on any proper facts,” Aleksandr Neradko said on Russian TV.
Egyptian President Abdel Fattah el-Sisi also said in an interview with the BBC that it was too early to say what had caused the crash.
He called a claim from jihadis allied to the so-called Islamic State (IS) group that they had brought down the plane “propaganda”.
“This is one way to damage the stability and security of Egypt and the image of Egypt,” he said.
James Clapper, the US director of national intelligence, said there was no “direct evidence of any terrorist involvement yet” adding: “It’s unlikely, but I wouldn’t rule it out.”
Russian President Vladimir Putin has described the crash as an “enormous tragedy” and expressed his condolences to the families of the victims.
“Without any doubt, everything must be done to create an objective picture of events so that we know what happened and can react accordingly,” he said.
At a news conference in Moscow, the deputy director of the airline, which was later renamed Metrojet, ruled out a technical fault and pilot error.
“The only for the plane to have been destroyed in mid-air can be specific impact, purely mechanical, physical influence on the aircraft,” Alexander Smirnov said.
“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.
However, the widow of the plane’s co-pilot told Russian TV her husband had complained about the aircraft’s technical condition.
The Airbus 321 lost speed and started descending rapidly, and the crew made no attempt to get in contact and report about the situation on board, Mr Smirnov added.
The bodies of 144 of those killed in the crash have been flown back to the Russian city of St Petersburg, where the plane had been headed from the Egyptian resort of Sharm el-Sheikh.
Russian Emergency Situations Minister Vladimir Puchkov said that searches in a 20-sq-km (7.7-sq-Mile) area around the crash site had ended and that a 30-sq-km area was now being searched.
Mr Puchkov said searches would not end until all the bodies have been recovered, AP reports.
The plane was carrying 217 passengers, including 25 children, and seven crew members – mostly Russians.
Timeline: the course of flight KGL9268
05:58 Egyptian time (03:58 GMT): Flight leaves Sharm el-Sheikh, a statementfrom the Egyptian cabinet says
06:14 Egyptian time (04:14 GMT): Plane fails to make scheduled contact with air traffic control based in Larnaca, Cyprus, according to Sergei Izdolsky, an official with Russia’s air transport agency
06:17 Egyptian time, approx (04:17 GMT): Plane comes down over the Sinai peninsula, according to Airbus
11:12 Egyptian time (09:12 GMT): Flight had been due to land in St Petersburg’s Pulkovo airport