I've long wondered, and I now seek your wisdom on: Why do airlines offer direct flights? (e.g. UA1178, which goes BOS-EWR-IAH-SFO, or UA123 BOS-IAD-SEA-SFO) What's the benefit to them? My own frustration is that UA awards miles based on the end-to-end distance, ignoring stops, whereas taking flights with different numbers through the same connection point would earn separate miles on each segment. Yet there's no upside: legacy-UA would often (usually?) have a plane change for each segment, and even when they don't change planes, they make all passengers deplane. Southwest, of course, does something different, allowing passengers to stay on board. Posted here rather than in the UA forum since it seems like a more general question; feel free to move it if appropriate.