I'm taller than average so it already sucks but last year I had three flights IN A ROW where I got placed behind somebody who was obsessed with leaning back in their seat. Like they'd lean back as much as the seat would let them which was already painful but then they'd try and push it more and more and jump back into the seat which was only hurting my knees more. One was 6 hours and I literally could not sleep 1 second because of the pain. three DIFFERENT people did this! Noise cancelling headphones did not help.