Planes flying rely on the thrust of engines to overcome drag/air-resistance and the aerodynamic forces on the wings to overcome gravity. When the velocity of the plane is too low, the wings produce insufficient lift and the plane is said to “stall”. It’s hard to imaging stalling at 700 km/h but at high altitude the air is so thin the speed required to maintain lift is very high.
When instrumentation failed, the pilots lost control of the aircraft and could not recover from the stalled condition. The plane descended rapidly and crashed several minutes after the stall began. It seems several things went wrong together preventing normal operation of the plane. Normally, instrumentation permits pilots or automated systems to recover from a stall but without proper information about attitude and speed and at night with no visual cues it is extremely difficult. This is a preliminary report with a more detailed analysis to take weeks.