I realize this isn't strictly an Alaska Airlines topic, but checkpoint 5 at SeaTac is basically an Alaska Airlines security checkpoint since it's the general use one closest to the D and N gates.

It closes November 4th at 8pm. For at least 12 months. Your alternates, if you don't have TSA PreCheck, are checkpoint 3, checkpoint 2, and checkpoint A (when open on peak travel days). If you have TSA PreCheck then checkpoint 4 is a great option.

The port has an updated flythrough of the gateway project, which includes renderings of the new checkpoint 5, if you're curious to see what it'll be like when finished.