I'm sure that they'd be using a better system if one existed. Flying without airspeed is relatively simple, and many airlines practise it. The systems are normally at least triplicated...sometimes more.
Think about what you are trying to measure? Airspeed is a measure of the local airflow over the aircraft. For an aircraft moving at exactly the same speed through the air, the airspeed will vary with altitude (i.e. constant IAS varying TAS). A satellite system (i.e GPS speed) is a measure of your groundspeed. It is of no use whatsoever for actually flying the aircraft. In any event aircraft have innumerable speed displays and systems. Within a few seconds, I can be looking at IAS, TAS, G/S, GPS speed and IRS speed. Only IAS makes the wings work. TAS corrected for wind gives me G/S. GPS and IRS are showing G/S worked out in slightly different ways.
