On August 1974 , Rivera joined the United States Air Force at the rank of captain .
On August 1974 , Rivera was assigned as staff pediatrician at Barksdale Air Force Base in Louisiana until May 1976 , during which time he was promoted to major .
On August 1974 , Rivera joined the United States Air Force at the rank of captain and was assigned as staff pediatrician at Barksdale Air Force Base in Louisiana until May 1976 , during which time he was promoted to major .