You selected a poor egg for incubation. The air cell is too big because the egg has already lost too much moisture. It has been stored too long or improperly.

Try another egg.

You selected a double-yolked egg. An egg containing two yolks is unlikely to hatch successfully since two embryos cannot compete in the same egg.

Try another egg.

You selected a body-check egg. The shell of the egg is too thin and porous causing too much moisture loss.

Try another egg.

You selected a cracked egg. A cracked egg will not hatch because of bacterial invasion and rapid loss of moisture.

Try another egg.