I have three 2.5 - 3 week old chicks and yes, they can fly. WOW. It's only to the top of the brooder (54 gal Rubbermaid bin), and only one of them does it regularly right now. She flies up there whenever I come into the bathroom (only safe place to keep the brooder). She'll turn around, then sidle along the top of the bin until she's about six inches away from me, and turn her head back and forth to look at me from each side. After 3 or 4 minutes, she's satisfied and will sidle back down to the end of the bin to jump back into it.
One of the others has flown/jumped up there, but it was after a fly..... she wobbled on the edge for a few seconds, then turned around and jumped back in.
I know that one of these days I'll discover a bathroom full of chickens. I added four 3 day old chicks this past Friday.
I also handle all the chicks a couple of times a day, trying to get them used to me. They don't startle when I come into the bathroom any more, but they DO NOT like to be picked up. I find it interesting that Rebecca (the Plymouth Barred that is the flyer right now) seems to fly up to check me out. The last time, she vaulted to the top of the waterer and launched from it.
I don't want to cover the bin with screen, but neither do I want to find chilled chicks outside of it!