I finally got an Air in my hands the other day at an Apple Store. It did feel very nice and light to hold, and the sheer size of the thing actually makes it feel lighter than you'd expect it to feel. And I could imagine the general thinness making it disappear in my pocket a bit better. But to me, that screen size is also a bit of a negative for one-handed use.
With my 15 Pro held up with my pinkie forming a "shelf" (as one does) I can get my thumb to reach almost to the top of the display and reach most UI elements. But with a screen the size of the Air, there's just no way I'm going to reach the top one-handed. And while the Air is light enough to juggle it a bit in the hand, IMO it's still out of one-handed use territory without really risking dropping it. For me anyway.
Sadly, I think my ideal phone is as thin as the Air, but a bit smaller. And I'm sure that smaller size that would bring even more compromised battery life, so we will not see it. Maybe someday.