Tiredness
I'm interested, and somewhat relieved to find that some of you "youngsters" also feel knackered after being airborne for a couple of hours. I assumed it was my advanced years that made me feel so tired straight afterwards.
I can drive on busy roads/motorways for hundreds of miles, and for several hours at a time without feeling really tired. You might think that driving at motorway speeds, on roads as crowded as they are today might be just as tiring as flying, but it seems that being "up there" brings stresses over and above those that are found "down here", even though to a large extent, they are not prominent at the time.
God knows what state I'm going to be in after the GFT!!!