I am researcing the area to pprleory provide alienjesus with an answer (not nessecarily THE answer) and will return to the subject with an extensive report either here or on notaw.com. In the mean time, could you make some observations for me concerning the density of the vapour trails? The denser they are, the higher up the aircraft flies. For instance, max cruise height for 737s and 747s is around 41-42000 feet. Airbus aircraft generally cruise slighly lower at 37.000 38.000 feet, again all this depends on the specific fuel configuration. Anything flying higher than 42.000 feet is most likely military. Sometimes you can even make out how many engines the aircraft may have by looking at its vapour trail.Anyway, more later. If you want detailed information about the current flying condition in the Phoenix area this is a good starting point.

I actually found this more enetratining than James Joyce.