Ada was mandated by the DoD for a bit. My understanding is that, in practice, this involved making a half-hearted effort in Ada, failing and then applying for a variance to not use Ada.
Often, I'm sure, but there are large code bases in Ada still. It's a shame, it looks like a really great language I would love. But it's a chicken and egg problem. If only Mozilla had decided on Ada instead of Rust! :-)
I actually met a programmer who worked on military jets. According to her, Ada is only used anymore for the older jets that were already programmed in it, and she worked in C++.