Many of the infections associated with Lyme cause oxygen deprivation in the brain to varying degrees. Sadness, irritability, and confusion can all be symptoms of relative oxygen starvation. I never used to react like this, but the last 4 Winters I've had Lyme, skiing at our place in CO can exacerbate my cognitive and emotional symptoms. The link between mountains and airplanes would seem to be oxygen levels.
Obviously airplane cabins are pressured, but since our brains are already getting less oxygen than that of a healthy person, I think we are particularly sensitive to even slight decreases in ambient oxygen levels. I can see how even after a pretty short flight the oxygen levels would be slightly below what you'd get at or near sealevel.