It's always interesting to me how much experiences vary, and how likely it is that our biases also color our perceptions. Almost always when I get on a Delta flight (admittedly I fly them the most), I'll get a friendly hello and what seems like a professional and genuine smile when I get my beverage. My last few experiences on Southwest have been a borderline sneer (if any acknowledgment at all) as I get on the plane, followed by bizarre jokes over the intercom or a round of applause for the plane landing (?).