Russia on Monday sought answers for the latest deadly plane crash to raise concern about the safety of its civil aviation, with investigators focusing on a fault with the 23-year-old plane or pilot error as the likely cause for the disaster that killed 50. The Tatarstan Airlines Boeing 737-500 crashed on landing at the airport in the Volga city of Kazan after a flight from Moscow’s Domodedovo airport last night, killing all 44 passengers and six crew on board, the emergencies ministry said. ‘The main versions of what happened are an error in piloting and technical factors, including a technical failure,’ the head of the transport Investigative Committee for the Volga region Alexander Poltinin was quoted as saying. He confirmed that that the crash ocurred while the aircraft was making a second landing attempt and said the probe would have to consider why the pilot had not managed to land the first time.