Allow an old man to tell you a story. It might even be true.
Decades ago the USN standardized its shipboard computers: Unisys-designed and -manufactured AN/UYK-20/-44 (16-bit) and AN/UYK-7/-43 (32-bit) computers whose programming language was COBOL-like CMS-2 with cross-compilers written by Unisys, one of which was hosted on DEC's VAX/VMS. The USN also funded Softech to write and certify a VAX/VMS-hosted Ada compiler and runtime (ALS/N) for the 32-bit computers.
The Aegis Combat System (ACS), designed and programmed in CMS-2 by RCA and CSC, used five interconnected 32-bit computers running the Aegis Tactical Executive System (ATES). The computers' limitations constrained the design such that incremental changes took years to code, LBTS validate, operationally validate, and release to the Fleet.
To increase productivity, RCA and DEC developed a CMS-2 language sensitive editor for VAX/VMS followed by a CMS-2 compiler and runtime that enabled lab testing prior to LBTS validation of the CMS-2 code. About the same time DEC developed an Ada compiler and runtime that was interoperable with its CMS-2 runtime.
Unisys developed a series of demonstration programs running on VAX/VMS where Ada code invoked and exchanged data with CMS-2 code and CMS-2 code invoked and exchanged data with Ada code. Government engineers developed a transition path, with cost and schedule estimates, for introducing RCA and CSC engineers to Ada (using the Intermetrics PDL processor), for introducing Ada incrementally and safely into the ACS, and for hosting an ACS-constrained subset of the ALS/N runtime on ATES.
The programs were live-demonstrated to the shipboard computer program manager, the ALS/N project manager, the shipboard computer policy manager and a Navy officer representing the Aegis program office. The fully successful demonstration was followed by presentation of the transition path.
The ALS/N project manager said ATES must be replaced by the ALS/N runtime.
The shipboard computer policy manager said the entire ALS/N runtime must be implemented for certification.
The shipboard computer program manager said ALS/N was the future.
The Aegis program office representative showed polite interest in the demonstration and the transition path.
The ALS/N project manager, shipboard computer policy manager and shipboard computer program manager left USN employment within the year. The Aegis program office representative moved on to her next assignment. The CMS-2 life cycle maintenance was essentially moved into the care of the Aegis program office. And ACS's increased capabilities (eg, BMD) were achieved with "adjunct processors" programmed in C for many more years.