I cannot think why anyone would oppose a change from 5 on 3 off which is the most eficient way to roster most categories of airline staff including pilots to a 5 on 4 off, which is clearly more desirable socially. Unless, of course it is associated with a change in the planned flight schedules. Perhaps it is associated with a change in the mix of earlies/lates. Perhaps they are planning even earlier departures and even later arrivals back at base. If that is so the extra day off might be an illusion. But if Ryanair could get a better ownweship to flight cost ratio in that way it would be yet another cost reduction for them. I think this issue has a long way to run.