All the above explanations are really very useful. I have just start know to fly on the 737, and I would like to ask you an other thing. How long does it take to decrease speed? I read 10kts for nm, but this is true only in level flight. So if you are in lvl change and you star to reduce, it will assume a ftpm of 500/1000, and how long will it take to decrease? I suppose less than 10kts for nm? Somone can help me?thanks a lot