I don't even take jeans with me anymore when traveling. They take up too much space in the bag, and are always setting off the detectors, so for me it's a business casual look unless it's some type of meeting where I need a suit, but I'm likley to have the tie in my jacket pocket until I land.

Once I started getting upgraded fairly frequently, I do try to look a bit better for flights, shave first, all that stuff, so I guess you could say I do dress better on the hope of moving up front.