I'm no expert- not at all- I have 13 chicks- only one that I've hatched myself, who is now 10 days old.
I was shipped 15 eggs from Florida (I'm in Maine)
Perfectly packaged.
6 of the eggs were broken in the box (don't ask me how--- they were so well packed- I think the USPS played kick-box that day)
2, I later found, were actually broken, but such fine cracks I didn't notice until I candled them.
I have no idea how to check to see if air sacs are intact, so don't know if they were or not.
Incubator (still air LG) spiked and dropped temps several times
AND, it was my first hatch.
1 chick hatched on day 21, and nothing else.
As far as I'm concerned, it was a super result considering all the odds were against this hatch.
I do say, I blame the USPS for most of the failure, however!