I plan to book the red-eye UA770 SFO-BOS (operated on 752) on 11/27 (the Sunday after Thanksgiving). I was surprised to see that in the E- section, row 22-39 were booked out (one seat open in row 39 ), and only row 40 is completely unoccupied. There are only 6 seats occupied in E+ and F is completely empty. The fare inventory shows F9, A9, Y9, B9, M5, and the other classes are 0. I am curious whether the seats were really booked out or blocked for later release. If there is no possibility for lower fare inventory to be released, I might have to book a standard award. UA506 LAX-BOS on the same night is also F9, A9, Y9, B9, E9, U9. Not many seats left in E-. Any suggestion is appreciated.