>planes use most of their energy to not crash into the ground Surprisingly, not by much! To the first approximation an optimized plane will use 50% of its pow

>planes use most of their energy to not crash into the ground Surprisingly, not by much! To the first approximation an optimized plane will use 50% of its power during cruise generating lift ("not crashing into the ground"), and 50% of its power overcoming drag.[1] The tie is broken because planes expend extra more energy climbing than they save descending, and that's also part of "not crashing into the ground." :) [1] http://www.withouthotair.com/cC/page_272.shtml http://www.withouthotair.com/cC/page_272.shtml