What if air is trapped in brake line?

If air is trapped in the air line then ost likely its winter time and moisture and debri has accumulated in the air line causing a blockade. You could try and melt the ice in the air line, or you could do what I would do and get a rock and hit it until the stuff in the air line broke apart, but, if your really in a hurry toy wond mind paying for a new air line.

Just try not to use your parking brakes during the winter time. You know what I mean.