The crash, in Egypt's Sinai Peninsula on Saturday, could only have been the result of some other "technical or physical action" which caused it to break up in the air and plummet to the ground, said Alexander Smirnov, deputy general director of the airline, Kogalymavia.
He did not specify what that action might have been, saying it was up to the official investigation to determine.
"The plane was in excellent condition," Smirnov told a news conference in Moscow.
"We rule out a technical fault and any mistake by the crew," he said.
He said there had been no emergency call from the pilots to services on the ground during the flight, which took off from the Egyptian Red Sea resort of Sharm el-Sheikh and was bound for the Russian city of St Petersburg.
Kogalymavia's deputy general director for engineering, Andrei Averyanov, said a 2001 incident when the plane's tail section struck the tarmac on landing was fully repaired and could not have been a factor in the crash.
He said the aircraft's engines had undergone routine inspection in Moscow on Oct. 26 which found no problems and he said in the five flights before the crash, the crew recorded no technical problems in the aircraft's log book.
Oksana Golovina, a representative of the holding company that controls Kogalymavia, told the news conference the airline had experienced no financial problems which could have influenced flight safety.
Russia PM Medvedev calls for detailed investigation
Russian Prime Minister Dmitry Medvedev called for a thorough investigation.
"The key task is to investigate in detail what caused the tragedy," Medvedev said in remarks showed by Rossiya-24 state television.
First bodies from Egypt plane crash arrive back in Russia
The first bodies from the plane crash arrived in St Petersburg aboard a Russian government plane.
The crashed Airbus A321 plane, operated by Russian airline Kogalymavia, was carrying holidaymakers from the Red Sea resort of Sharm el-Sheikh to St Petersburg when it crashed in the Sinai Peninsula on Saturday morning. All 224 passengers died in the crash.
Russian news agencies reported that a first Il-76 Emergency Situations Ministry plane flew into St Petersburg's Pulkovo Airport a little before 6 a.m. local time, carrying 144 bodies.
The ministry said the next plane carrying bodies would leave Cairo on Monday evening for St Petersburg. On arrival, the first bodies were loaded onto stretchers and carried into a large white lorry waiting on the runway at Pulkovo Airport.
People light candles during a day of national mourning for the plane crash victims at Dvortsovaya (Palace) Square in St. Petersburg, Russia. Source: AAP
A Reuters photographer then saw the white lorry leaving the airport, escorted by police cars. It was heading for a St Petersburg morgue, where the bodies were to be identified.
The identification process was meant to start around 11am local time.
At Pulkovo Airport on Sunday, grieving Russians piled flowers high in memory of their dead compatriots. Mourners in Moscow arranged candles to spell out 7K-9268, the number of the flight that crashed.
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Russian jet 'broke up mid-air'
Russia and other former Soviet republics have poor air safety records, notably on domestic flights. Some accidents have been blamed on the use of aging aircraft, but industry experts point to other problems, such as poor crew training and lax government controls.
St Petersburg authorities have decided that official mourning events will last until Tuesday in Russia's second city.
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