An air sac is usually a good sign. Does the yolk move round the egg when you turn it to candle? Could you post a pic? I wouldn't give up on them just yet some eggs don't show signs of developing untill further along in incubation. Shipped eggs are harder to hatch due to the fact they can become damaged and have misshapen air sacs. Do your air sacs look mishapen?
This is a good read if your incubating shipped eggs. Sometimes there is a little movement with the yolk but it shouldn't follow you all the way round the egg really. Yes large air cells are a sign that they are damaged/ misshapen. Incubating them in cartons or set in a turner very upright with fat end up can sometimes help. Shipped eggs are hard to incubate usually have less than 50% hatch rate.