Alternative to Ada is often writing Ada in some other language more painfully :( I think it's sad that companies move to restricted C/C++ subset just because there are more people with C/C++ in their resume.

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