From Jeff Findley:
stmx3 writes:

Jan C. Vorbrüggen wrote:
The people writing the Shuttle avionics software are one of very few -
maybe three to five - groups rated as "Level 5" by the Software Engineering
Institute - in fact, they're somewhat of a role model for that level.
No comparison to Redmond et al., who are around level 1 or 2.

Impressive! That speaks volumes as to the complexity of the code they
have had to deal with.

Not really. This has more to do with your software development
processes and how you continuously improve it. It doesn't really
matter if you're applying these processes to shuttle avionics, a word
processor, or an operating system.

http://www.sei.cmu.edu/about/about.html

I would agree that the chances of a shuttle crashing due to a software
glitch is very small. The point was why take a chance when you have
proven flown software available? It becomes a risk trade with any
potential safety gains in the new version.


~ CT