The "Guru of Advanced Thinking About Advanced Radios" of Rockwell-Collins
gave an interesting talk at the Cedar Rapids Central States Conference a few
years ago.

One point he made was that (even) Collins had to buy enough chips for their
complete expected production run, and eventual spare parts, right at the
design-in stage. Otherwise either -

1) The part would be unavailable before the production run was completed, or
2) A part with the same number would be available, but it would be enough
different that it would either not work or would degrade performance.

Even the Big Boys have parts problems.

73 de bob w3otc