A US air force F-16 jet based in Italy went missing off the Adriatic coast on Monday.
Italian news reports say the pilot's last communication to Aviano air base reported a problem with the plane.
The fighter plane was flying in formation with other jets when it lost contact with the control tower.
Italian news agency ANSA reported that the pilot's last contact was at 1900 GMT.
AFP reported that Aviano did not confirm the news, nor did Italy's coast guard comment on the incident.
The Italian coast guard is conducting search-and-rescue operations off the coast where it is believed the pilot went down, reported Reuters.
Aviano is a NATO air base administered by the United States north of Venice, Italy.
The base hosts the US Air Force's 31st Fighter Wing.
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