The question was about the Delta/Western merger, not the PanAm acquisition.
DL/WA was a straight DOH merger for the FA's. In fact, there were some Western Inflight supvs/mgrs who were NOT FA qualified. DL required them to get qualified, and they were given a line seniority position at the bottom, as a a new hire FA, they were not integrated. WA flight attendants were unionized, however the union did not have any right to represent the former WA emplyees after the merger.
As for the PA aquisition, yes the top 3000 DL F/A's were protected. However, the most junior PA FA was protected by being placed at least 3000 above the bottom. I was in the bottom 3000, I went from 15900 in seniority to 18900 overnight. To the best of my knowledge, the lawsuit over seniority integration went nowhere. IMO, most of the former PA people should've been darn happy to get the seniority they did, especially after AA stapled the former TW people.