Hatching Rhea eggs.

[edmondsfarm]

Our male Rhea hatched a group of chicks and left us a nest full of eggs so we have been hatching them indoors and have 5 chicks so far. Of the eggs left one more looks ready The rest look like they were not fertalized. We can see movement inside when candled but the air space has gotten hugh (like 3/4 of the egg) and still has not begun to break threw. At what point should I attempt to help the chick? I would try to post a picture but need to look up how.