Originally Posted by npei

Empty middle seat in economy: between Platinum+ (window) and 1k + (aisle) is generally filled last after, all other empty middle seats fill between two lower or non-elite seat mates. This has been my experience flying as 1k for 20+ years and now lifetime GS (when I don’t clear upgrade). I even had it happen 2019 when my empty E + middle seat next to me was the “last one standing” on entire economy class.

This has happened fairly frequently (50%) even post-Covid travel recovery when most-all middle seats are increasingly filled. My last 6 UA flights in 2Q2024, 4 transcon SFO-IAD, and 2 international SFO-TPE segments, there were 3-6 empty middle seats in economy in each flight that I didn’t clear upgrade and was seated in aisle E +. As I watch T-1 and after checkin, I see that some E + and E - middle seats are filled by last minute purchases or standby requests, while 50% of time empty E + middle seat is open next to my aisle seat when flight takes off. When I ask my window seat mates if they are Platinum or 1k+, invariably it’s always yes when our E + middle seat is open.

Originally Posted by Repooc17

I have not observed middle seat protections for higher elites. I have been on too many flights where E+ is full but not E. I have lost count on the number of flights between EWR and SFO where multiple E+ middles were open but never in my favor; did not matter if I'd picked front, middle, or back sections of E+.

I have now resigned on BE tickets when flying UA partly due to above, and surprisingly coming away with better flying experience, including free selection of E+ on certain flights, even with a BE ticket.