Pratt & Whitney, purveyors of jet engines for civilian and military applications, did a study on this many years ago, without actually intending to do the study.

They went on the same metrics kick everyone else went on in the 1990s. They collected a bunch of data about their jet engine controller projects, including timecard data. They crunched it. The poor sap who got to crunch the data noticed something in the results: the military projects uniformly had twice the programmer productivity and one/fourth the defect density as the civilian projects.

This, by itself, is significant. It means you only need half as many programmers, and you aren't going to spend quite as much time fixing bugs. What is even more important is that this was an apples-to-apples comparison. A jet engine controller is a jet engine controller.

He then went looking for candidate explanations. All of the usual candidates: individual experience, team size, toolsets, software processes, requirements stability, everything, were trotted out, and they were ruled out when it was seen that the story on those items was uniformly the same on both sides of the aisle. At the end of the day, only one statistically significant difference showed up.

The civilian projects were written in every language you could think of. The military projects were all written in Ada.

IN EVERY SINGLE CASE, against every other comer, for jet engine controllers at Pratt & Whitney, using Ada gave double the productivity and one/fourth the defect density.

I know what the flying code monkeys are going to say. "You can do good work in any language." In theory, that's true. In practice, however, it appears that, at least at Pratt & Whitney, language made a difference.

Last I heard about this, Pratt & Whitney upper management decreed that ALL jet engine controller projects would be done in Ada.

No, I don't have a citation. No paper was ever written. My source on this story was the poor sap who crunched the numbers.

This, incidentally, was BEFORE Boeing did the 777, and BEFORE the 777 brake subcontractor story happened. But that's another story.