Writing on an airplane is HUGELY productive. An expensive habit. Is it the boredom? Disinterest in the in-flight movie, especially compared to the delights of parsing the safety video? Sustained physical discomfort resulting in yoga-ish inward journeys? Mid-conscious realization that flight in a huge metal tube at lethally cold low-pressure altitudes is an hours-long defiance of the designs of Nature, and Nature ALWAYS wins?