The announcement came in a statement on the internet accompanied by pictures of his driving licence.
"Your brothers in Al-Qaida in the Land of Two Rivers got their hands on a US pilot who turned out to have bombarded several mosques and the Sheraton hotel in Baghdad during the invasion of Iraq, as well as several civilian homes," according to the statement on Sunday.
It said that "after questioning this infidel, the divine verdict was applied to him".
The statement, whose authenticity could not be verified, did not specify the date of the kidnapping, but it was accompanied by pictures of an Illinois driving licence in the name of Neenus Y Khoshaba, born 27 November 1948.
There was no immediate comment from the US military.
The group led by al-Zarqawi, Iraq's most wanted man with a $25 million US bounty on his head, has claimed a series of devastating attacks as well as kidnappings since the April 2003 fall of the Saddam Hussein government.