The 737 fuselage is closely tied to the previous generations of Boeing jets like the 707 and 727. It inherited the eyebrow windows above the main cockpit windows. These days, the controlled airspace has made the need for these while maneuvering a lot less. Current jets are built without them and many airlines have reduced maintenance costs by plugging them. I had assumed that they had gone away for most operators. Apparently not for Alaska! Walking through the terminal, I saw one jet with the eyebrows and was surprised. However, then I saw a bunch more so clearly this is still something Alaska see as valuable.