For the interest of the non pilots here, when I was trained I was taught that should one encounter exteme turbulence in the cruise, you should ignore airspeed and altimeter readings, leave the cuise power as set and just use the controls to maintain the normal cruise aircraft attitude.
I was also taught that if one lost airspeed indication in the cruise you should do the same thing - leave the power as set and maintain attitude.
Of course I do not know what is taught these days.