Data Point: Southwest.
Situation:
Five of us flying BOS-CUN (via BWI) and then returning CUN-BOS (also via BWI) next month.
Used points and companion pass for all; reserved back in June.
SW eliminated the CUN-BWI flight and rebooked us on a flight 2.5 hours earlier.
This change not only shortens our last day of vacation in Cancun but also leaves us with an almost 4-hour layover in BWI.
All other flights that day are now sold out.
Resolution:
Southwest customer relations offered, and I accepted, $75 voucher per person (that's $375).
I'm pretty happy with that outcome.