dCLbydalpha
The airworthiness authorities basically demand it. In reference to the example, how many combined GPS/Inertial sensors are certified by a civil air authority for navigation?
There is a lot of work in this area - and QANTAS and Honeywell are in the lead on it: See this ICAO document one of many -
https://docs.google.com/viewer?url=h...%2F6104_en.pdf