Nicholas Murphy, of Exeter, Rhode Island, pleaded guilty on Monday to one count of traveling to engage in illegal sexual activity with a minor.
Court documents show Murphy started communicating with the girl through social media.
Police say Murphy drove to Connecticut and picked up the victim without her parents' knowledge. She was reported missing Sept. 17, 2015.
In a petition to plead guilty, Murphy wrote he was "truly remorseful." He faces a maximum of 30 years in prison during his sentencing hearing scheduled for Sept. 13.
It's not clear if Murphy is still an active member of the Air Force.
