I believe I read elsewhere in the forums that an aircraft battery can be drained if the starter has been left on ‘start’ and the avionics subsequently go off. The fix or work-around being to ensure the starter is disengaged after starting the aircraft.
I cannot understand why there would be any connection between downloading content and a crash during flight?
I will take a bit of stab in the dark though: is it potentially because you have been on a long flight perhaps on autopilot but have not interacted with the controls/console… therefore the Xbox is trying to enter into a power saving mode causing the sim to quit/crash?