Why would this be a sign of arrogance, disrespect, or anything else for that matter? I do not always acknowledge every crewmember I walk by in the terminal either, so what? Think you're reading too much into this one. Alot of the time I'm probably just too engrossed in my own thoughts or just thinking about food or something that I don't notice. I highly doubt most co-workers in any job always nod to each other when they walk by.