Earlier in the week we land 10 minutes early at SFO, as we taxi in they announce some people in the back have a very tight connection, could everyone without a connect please wait and let them out first. So how do they have a tight connection if we land early?

I thought legal minimum connection time were at least 30 or 45 minutes. I understand if there was bad weather/delays anywhere, we landed in Term 1 (not Term 3) or we were late, but this truly baffled me. I asked the FA and she said she had no idea. The only thing I can think of is UA booked them a connection into a flight leaving from Term 1?? Any other ideas?