It's a very popular travel day, so that might be part of it. That said, unlike DL, where there is a very high correlation between revenue fare pricing/class availability and award pricing, AS seems a lot more random. Possibly because DL assigns an award class for every revenue fare class (NV = V, NX = X, NT = T, and so on). While class availability in DL award buckets is not always identical to the corresponding revenue buckets, they usually match. You can tell from below there is 1 seat left in DL revenue X class on flight below, and also 1 seat left in corresponding NX award class. If you attempt to purchase 2 or more seats on the following flight, it will bump up both revenue and award pricing (to T class fares and NT class awards).