Thanks for the explanation and for the link as well. But when the air is saturated at high altitudes then why wouldnt the excess water vapor become visible (clouds to form everywhere in the sky). Also, the 737 states not to use anti-ice when SAT is -40 or below (high altitude). I can explain this its the air at temp -40 or below that cant hold more water vapor because the air is saturated.. But wait, since the air is saturated wouldnt the excess water form an ice also?