Coming from someone who's done embedded work (although nothing that's controlled an airframe), I have to say that methodology is much more important than language choice. Sure, choosing something that is deterministic and that you have half a chance of Proving Correct can help, but you're probably better off studying CMMI or Zero-Defect Software design[1]. Just as reference, the JSF (F-35) software is being written in C++ by the DoD, although that group is one of the few CMMI level 5 groups in existence. While I personally hate CMMI, I have to admit that it is one way to ensure an organization is accountable and ticking all the checkboxes.

That being said, avoid PHP, Matlab and C# at all costs if safety is at all important to you.

[1] - http://www.amazon.com/Toward-Defect-Programming-Allan-Stavel...