One of my colleagues had a case of unreliable airspeed on the 757. Ably coped with by pitch/power flying. Not to be discounted is the severe disorientating effect of high speed warnings with zero airspeed, and stick shaker with absurd high speed readings, klaxons and warning lights. It is a time to try and calmly stick to basics. Certain recent past accidents could have been prevented by focusing on the right information-INS groundspeed is near enough TAS to keep you alive. It will be rare to lose all visual references which could help- at night time staying near illuminated areas might assist in retaining orientation