Very good advice here !
Everyone.. PLEASE pay attention to when the "internal"
pip has occurred, easy to tell if you monitor the eggs during incubation.
The larger end is the air cell end and will be tilting UP IN THE AIR until internal pip has happened, usually 1-2 days pre " due date ".
Once the " internal pip" has happened
the egg will sit level and hatch out should happen within 48 hours.
The chicks in those shells have enough air...."AFTER" the internal pip has happened.... for 2 days max.
When it's getting close to 48 hours "AFTER" the internal pip has happened
and no external pip has been made ..then, and only then...should you intervene and make a very tiny air hole with a Sterilized tool in the air cell end.
Just enough to get the chick air is all. After that leave it alone, that chick needs to do ALL THE WORK ON IT'S OWN in order to work the yolk sac in fully, etc.