In message , at 15:18:36 on Sat, 28 Oct
2017, Recliner remarked:

It seems that even back then, airlines had alliances, but were more
open about code-shared flights than they are today.

https://www.flightstats.com is pretty transparent about codeshares. It
even tells you which company operates the flight (rather than markets
it).

eg: "Operated by (YV) Mesa Airlines on behalf of (AA) American Airlines,
a codeshare flight by the following airlines:
(GF) Gulf Air, (AS) Alaska Airlines, (BA) British Airways"
--
Roland Perry