McCain was born on August 29, 1936, at the Coco Solo Air Base in the then-American-controlled Panama Canal Zone.
From the US State Department website at http://www.state.gov/documents/organization/86755.pdf
7 FAM 1116.1-4 Not Included in the Meaning of "In the United States"
a. A U.S.-registered or documented ship on the high seas or in the exclusive economic zone is not considered to be part of the United States. A child born on such a vessel does not acquire U.S. citizenship by reason of the place of birth (Lam Mow v. Nagle, 24 F.2d 316 (9th Cir., 1928)).
b. A U.S.-registered aircraft outside U.S. airspace is not considered to be part of U.S. territory. A child born on such an aircraft outside U.S. airspace does not acquire U.S. citizenship by reason of the place of birth.
c. Despite widespread popular belief, U.S. military installations abroad and U.S. diplomatic or consular facilities are not part of the United States within the meaning of the 14th Amendment. A child born on the premises of such a facility is not subject to the jurisdiction of the United States and does not acquire U.S. citizenship by reason of birth.
No Person except a natural born Citizen, or a Citizen of the United States at the time of the Adoption of this Constitution, shall be eligible to the Office of President -- The Constitution of the United States, Article II Section 1