The air sac starts to develop during storage HesterF. So the egg might have been in the tray upside down. We store ours in an egg carton and don't move them at all before incubation -never caused a problem. We have had air sacs at both ends, but the important thing is that the chick has room to manoeuvre and that's what the air sac gives it. I read once that it gives them a gasp of air, but I don't believe that at all. They can breath through the pipped hole. It may need help, because that's the strong end. But it will work around the side to create a large hole so it may not matter.
After we started breeding from our own eggs our only hatching failures were due to high humidity in the first 18 days (weather changed), bacterial infection due to running batches through the incubator without cleaning in-between and infertile eggs. We don't hatch eggs over 7 days old.