What beats me is why, in a new build jet, don't the systems recognise an unreliable airspeed, or an upset condition, and set a nominal N1 with A/T, command and fly a nominal pitch with F/D and A/P, fine tune it to level flight or a 100fpm climb using GPS altitude data and display a big F-O warning on the ADI saying something like 'AIRSPEED ANOMALY, LEVEL FLIGHT COMMANDED'
Why, when almost all parameters are known to the jet, and it has full capacity to control engines and flight controls, does the A/P just pack in when it's most needed?