ANSA reported a fuel slick was spotted off the coast near the Cervia Tuesday and a fishing vessel came upon carbon fragments that could belong to the jet.
The aircraft, assigned to the 31st Fighter Wing at Aviano Air Base, was on a training mission over the Adriatic when the base lost contact with the pilot Monday night, the U.S. Air Force said.
Italian aircraft and ships were sent to the jet's last known location, U.S. military officials said.
"The search for and rescue of our pilot is our top priority," said Col. David W. Walker, commander of the 31st Operations Group. "We want to assure the family and friends of the lost Airman that we are doing everything we can for this effort."
Sources at Aviano's Pagliano e Gori airport, which has jurisdiction over flights from the U.S. air base, said there is concern a serious technical problem arose so quickly, the pilot "did not have time to activate the mechanism that makes it possible to eject, after having established that the plane could not cause risks for the local population."