Sleeping sitting up

The ability to sleep sitting up is considered a talent by some people I know. Indeed a number of years ago one public servant colleague of mine said that if he could sleep sitting up, work would be so much better. I have seen the odd chess player demonstrate this talent as well, although I assume not deliberately. The late Paul Dozsa was known to fall asleep at the board on occasion, and at a recent Sydney International Open there was a player both sleeping, and softly snoring.
Where such a talent would really come in useful is on long haul international flights. I am writing this while sitting in Abu Dhabi Airport, having just hopped off a 14 hour flight from Sydney. I'm pretty sure I got my usual 4 hours of airplane sleep, but I never really know. I am on my way to Bergamo, Italy for a small meeting of the FIDE Anti-Cheating Commision, which will take place over the weekend. Then it is back on a plane on Monday to repeat my sleeping experiments.