FThe load for 1920 LCY-GLA (and indeed the ZRH-LCY flight) was only about 25% I would say.
When I flew LCY-MAD on possibly the busiest weekend of the year for flights to/from MAD, the plane was only about 30% full. [Note I'm not saying that particular LCY-MAD route isn't sometimes busier.] Which made it particularly sad that everyone was so uncomfortable. Even just increasing the seat pitch by 3" (so taking out about 10% of the seats) would have made the whole thing bearable.