commercial pilots like brian smith also rely on color-coded weather radars to avoid nasty thunderstorms. but the strong winds that hit the united plane were invisible. >> if i can see it, it doesn't worry me at all, because i know i can go around it. it's what i can't see that i guess is more of a concern. >> it is possible to not see any problem ahead on radar and fly right through the middle of a massive rising column of air. >> reporter: tonight, all the injured passengers are home from the hospital. clayton sandell, abc news, denver. >>> and now, that banner headline around the planet, in social connection. we're talking about 500 million users on facebook this week. and as you'll see in a moment, we spent time today with the very young man at the center of it all, facebook founder mark zuckerberg. we got a look inside the headquarters. the heart of the revolution. but first, here's bill weir with more on the milestone. >> reporter: yeah, diane, this is the company that once fit inside a dorm room. but just over six years later, they have completely reinvented the way human beings i