Ada struck me as a language that would be a pain to write in(at least it would take a long time) but it was a pleasure to read. Even without an intimate knowledge of the language (I was a C++ guy) I was able to figure it out.
1. The JSF air vehicle C++ coding standards http://www.stroustrup.com/JSF-AV-rules.pdf
2. MISRA-C:2004 Guidelines for the use of the C language in critical systems http://caxapa.ru/thumbs/468328/misra-c-2004.pdf
3. MISRA C++:2008 Guidelines for the use of the C++ language in critical systems http://frey.notk.org/books/MISRA-Cpp-2008.pdf
Just check the archives.
Most likely because for writing fail safe software, it is better to use a language with built in support for safety, than using crutches.
But the real shocker is that you can't really write serious Ada for free, gnat is a pain, the free toolchain is a joke. My understanding is that there are good expensive private compilers out there. A few month back, I drank the cool aid and started a project in Ada, and the tools were a pain. The 'real time' system was ticking at a constant 1kHz. And making it tickless was looking tricky for a beginner. The formatting tool was bugging without an error message, the cross compilation toolchain for ARM is a pain, etc.