Rananim:
Turn off airway and DESCEND IMMEDIATELY
In the case at hand the captain should have ordered that the nose be lowered 15-20 degrees nose down and he should have reached over and set cruise-descent power while telling the pilots to ignore airspeed indications.
Although the turn off airway is the ICAO method, in this case it could have resulted in increased disorientation. Wings level was critical until a safe, stable configuration was assured.