Found it:Babies born at sea

A person born on a foreign vessel lying in U.S. port or sailing in the territorial sea of the United States acquires United States citizenship at birth. Howver, U.S. citizenship is not conferred upon a child was born to alien parents on a vessel bound for the United States which had not yet reached the twelve nautical mile limit. Similarly, a child born on a plane in the United States or flying over its territory would acquire United States citizenship at birth. However, the citizenship of the child is not affected by the nationality or registry of the vessel. Birth on U.S. vessel outside the territorial jurisdiction of the United States does not confer U.S. citizenship upon the child of alien parents.