...and don't forget the increase in mass due to aircrafts velocity in the Earths gravitational field. However, the E=W+Mc2 sh*t first really kicks in at speeds appraocing 60% of lightspeed, so no great operational concern
Concerning the particle / photon thread : would this mean that the aircraft would need to produce more lift during high altitude / high lattitude flight due to increased cosmic radiation level
And finally : Raising the cabin temperature would tend to expand the airframe, thus increasing form drag (and possibly friction drag due to expanding gaps in the airframe). So should complaints about low cabin temperature be answered by a curt: "You want to arrive on time, don't you, Sir"?
Now I cannot dream up any more variables affecting aircraft performance for the fly-f***ing department to consider - might as well go to sleep