I was speaking to some of my work colleagues about this yesterday: the less sleep you get while travelling, the weirder the ideas get. I thought it was something only I experienced, but apparently it's a generalised phenomenon. Since you can't sleep for whatever the reason (your body not wanting to switch to another timezone, or someone kicking your seat from behind with their knees), you stay awake.
You're not really able to do any productive work because we've already agreed that you're tired, and even if you try, more often than not you have to go back the day after, and fix all the "genius" errors you introduced while writing "clever solutions".
So your mind wanders. Very timidly to start with, but as you get more and more tired, at some point your brain just releases the "rationalising" brake and hey ho, it's all downhill from there. Crazy ideas abound.
For me (and I'm kind of scared that there's a pattern) these thoughts tend to be about piercings, tattoos and other variations of body harm. "Why do I want to get any of those since I know how long they take to heal?", I wonder when I've slept properly. But still, when you're 10000 feet high, everything seems like a good idea.
Your ideas? Share them, à la Sleep-deprived Anonymous style!