Isn't Ada precisely suited for this sort of application? What was the motivation for switching to C?

> What was the motivation for switching to C?

Invariably, cost. SPARK Ada is demonstrably superior to C for safety-critical development (I can't cite the sources for this, but a major company developing safety-critical software has shown this to be the case).

But, SPARK Ada requires a lot of highly skilled manpower and it's slow to develop. C gets the job done, albeit with lots of bugs.

If the industry is unwilling to invest in the training or tooling for a safe language like SPARK Ada, is there research into "easier" safe languages, something between C and Ada? Or do companies like Boeing still expect to be writing new avionics safety in C in 2030 or 2040?

Yes, Real-Time Java being an example.

Realistically, it seems to me that avionics etc. will be written in C for a very long time to come. It all comes down to the cost and availability of programmers.

C is incredibly portable and tons of programmers know it. Ada is great in a lot of ways but just never got the traction it needed to be #1.

Sure, but shouldn't safety be the number one concern here? Programmers can always be trained to learn it, as long as they demonstrate competence. It seems like an unfortunate case of trying to cut costs at the cost of safety.