Egypt has recovered the black box of a Russian airliner that crashed Saturday in the restive Sinai Peninsula, killing all 224 people on board, the prime minister's office said."The black box was recovered from the tail of the plane and has been sent to be analyzed by experts," the office of Prime Minister Sharif Ismail said, adding that rescuers had recovered 129 bodies from the site of the crash.Ismail later told a press conference that experts will "start examining the information in the black box, and based on this we will study the causes of the crash".The ISIS group affiliate in Egypt claimed it downed the plane, but without saying how. And Ismail expressed scepticism when asked about the claim."Experts have affirmed that technically planes at this altitude cannot be shot down, and the black box will be the one that will reveal the reasons for the crash," he was quoted by state news agency MENA as saying.In Moscow, Russian Transport Minister Maksim Sokolov too said the IS claim "cannot be considered accurate", adding that authorities in Egypt "have no such information that would confirm such insinuations".A senior Egyptian aviation official said the plane was a charter flight operated by a Russian firm, and was flying at an altitude of 30,000 feet when communication was lost.A senior Egyptian air traffic control official said the pilot told him in their last communication that he was having trouble with the radio system.The plane with 214 Russian and three Ukranian passengers, and seven crew, had taken off from the Red Sea resort of Sharm el-Sheikh in the south Sinai bound for Saint Petersburg. It lost contact with air traffic control 23 minutes later.The wreckage was found roughly 100 kilometres (60 miles) south of the North Sinai town of El-Arish, Egyptian officials said.