Interesting question. I have come across a few pilots, 10000H+ that have the same sensation. I must admit that 1000H+ later mainly flown 500' to 2000', I am starting to feel a little uneasy climbing above 3000'. Down under, we fly with all doors removed due to the heat factor in the cabin. Could it be an influencing factor? <img src="rolleyes.gif" border="0">