Search efforts continued off the northern Italian coast on Tuesday to locate a US Air Force F-16 fighter jet that went missing over the Adriatic Sea the previous day, a public affairs officer said.
"The search is continuing," an officer at the US base near Aviano where the jet was based told AFP.
The fighter jet was flying in formation with other aircraft when radio contact was lost on Monday.
The pilot had reported a problem in his last radio contact at 1900 GMT, the base said in a statement.
"While the aircraft has not yet been found, search teams are working under the assumption that the aircraft crashed in the Adriatic," it said.
Italian ships and planes have been sent to the area and are working together with the US military.
"The search for and rescue of our pilot is our top priority," Colonel David W. Walker, 31st Operations Group commander, was quoted as saying.
Traces of fuel were found floating in the water between the coastal towns of Lido di Savio and Cervia, the Corriere della Sera daily reported.
ANSA news agency quoted a local airport source as saying the pilot "would not have had time to eject as the malfunction was too sudden and too serious".