I have see UA reduce prices by opening up lower fare buckets (say Sunday shows Y9, S0. Tuesday shows Y9, S9 as a simple example). I assume this is to have a sale and move a few extra seats this week.

Does UA change the price of a bucket very frequently. I assume Y can go from $1000 to $800 because Southwest bought a gate. But does UA ever lower or raise fares for buckets just to push a few extra seats in the shirt run?