I still think to this day one of the best most opportunistic plays was United’s PanAm Pacific acquisition. Unlike some other mergers and acquisitions, this one returned a lot of value for many years thereafter and gave them the edge in the Pacific they still hold today (notwithstanding the pandemic issue).
The only other better plays in my opinion were the AA and UA Heathrow purchases, but they came at a much higher price
Perhaps the other one that was a great series of plays was AA’s various acquisitions that built the strong South American foothold and brand they have today
They were not liked by labor unions at the end of their runs, but Dick Ferris and Stephen Wolfe are two of the most important people in UA’s history. It was under them the airline went from a strictly domestic carrier to an international powerhouse and global airline. They deserve enormous amounts of credit for seizing the opportunity when it presented itself.
As you said, the PA Pacific routes still continues to be a crown jewel, along with having LHR long before CO, DL, NW, and US could ever go there. While AA got LHR from TW, they still had a split operation at Gatwick while UA was all LHR. Couple that with being a driving force in forming Star Alliance, they were truly the class of the USA based airlines abroad until 9/11. Those assets also helped them get out of a long bankruptcy by making the airline worth saving whole.