Aeroflot flight 1668, an Antonov An-24B, performed a regular flight from Yakutsk to Novosibirsk intermediate stops in Olyokminsk, Lensk, Ust-Kut and Krasnoyarsk. In Olyokminsk, the flight landed at 17:50 and took off at 18:10. At 18:20 the crew reported that the assigned flight level of 4500 m had been reached. Weather conditions along the route were favorable. At 18:28 the aircraft disappeared from the controller’s radar screen. It was found to have crashed and broken up in the taiga, 92 km from Olyokminsk. Presumable causes of the crash are: 1) due to unexplained circumstances, the aircraft went into flight modes that significantly exceed the maximum speed and overload limits; 2) separation from the aircraft of any part or parts, the impact of which caused the destruction of structural elements, presumably in the tail section; 3) a complex failure in the propeller-regulator-engine system, which led to a a loss of control with the subsequent destruction of the aircraft structure; 4) any failure in the aircraft control system.