I think it's possible that there could be other survivors. The back end of the plane broke off before the crash, so they could be somewhere.
I saw a screencap of the Spanish comic book the kid was looking at, and it showed a picture of a large, angry looking polar bear. This makes me wonder what's up with the kid -- whether he has "powers" or something, or if things are connected to him somehow. Also, his dad said he'd find the dog as soon as it stopped raining, and it stopped immediately. I wonder if there's something to that.
ETA: Here's the picture:
