Answer:
I am lighter than air, but a hundred people cannot lift me. Careful, I am fragile. What am I?
I am constantly overlooked by everyone but everyone has me. What am I?
I am a path between high natural masses; remove the first letter to get a path between man-made masses.
What can you lose that will cause other people to lose theirs too?
I am a protector. I sit on a bridge. One person can see right through me while others wonder what I hide.
They're actually great swimmers now, but later they will become excellent hoppers.