So even if the flight is truly 1/3 full (since presumably your "connection" is someone work works for UA who can see currently booked loads), do you know what fares those ~60 people booked into? What if 20 of them already booked that K fare? Do you think UA wants to sell all the seats on this flight at 97.20? Obviously not which is why they use the fare buckets to control their revenue. If only U is available currently, they're betting they don't need to sell anything less than U fares to get this flight full by the time of departure, as it continues to get closer they can adjust that if their prediction ends up being off. But given they have K filings gointo to 14 days advanced purchase, L filings as close as 7 days adv purchase, and T filings as close as 3 days advance purchase, they have plenty of options to open lower fare buckets closer in, if their prediction ends up being off, without going all the way down to selling additional K fares.