That first bit isn't quite true. At a given altitude, a specific attitude and thrust setting will maintain constant altitude and velocity. Obviously it's much

That first bit isn't quite true. At a given altitude, a specific attitude and thrust setting will maintain constant altitude and velocity. Obviously it's much more complicated than that, but this is taught to pilots (although not included in their re-certification tests, as noted by the BEA). With properly trained and tested pilots, loss of airspeed indication is a completely survivable incident, and in fact many planes have suffered such incidents at altitude without accident.