Alessandro Garofalo / Reuters, file

A U.S. Air Force F-16 fighter jet like the one shown flying over Aviano Air Base, Italy, is presumed to have crashed in the Adriatic Sea while on a training exercise. Aviano controllers lost contact with the plane about 8 p.m. local time Monday.

U.S. and Italian authorities searched the Adriatic Sea on Tuesday after a U.S. Air Force fighter jet was lost and presumed to have crashed.

Divers focused on waters where a fishing boat had found fragments believed to belong to the F-16, a Coast Guard official told Reuters.

Fragments of carbon steel and other debris were found floating in the northern Adriatic overnight, Rear Admiral Francesco Saverio Ferrara told Reuters. The U.S. Air Force said in a statement it believed the debris belonged to the wreckage of the missing aircraft, Reuters reported.

"We hope to find out more during the day so we can have a more complete picture of what happened," Ferrara said, according to Reuters.

Controllers lost contact with the F-16 at about 8 p.m. local time (2 p.m. ET) Monday, after it took off for a training exercise from Aviano Air Base, Italy, the Aviano-based 31st Fighter Wing said in a statement.

Italian aircraft and ships were dispatched to the missing jet's last known location, and U.S. and Italian aircraft were flying over the area Tuesday, the Air Force said.

The Italian national news agency ANSA reported that a fuel slick was seen off the coast near the town of Cervia and that a fishing boat had found fragments that could have belonged to a military jet.

Weather was bad at the time the plane vanished, with sleet falling and visibility poor, the Associated Press quoted an Italian coast guard commander as saying. 

The Italian news agency LaPresse reported that the pilot sent an alarm signal to Aviano before contact was lost and that three other planes on the training mission had made it back to the base safely.  

No information was released about the pilot, who was the plane's sole occupant.

Search-and-rescue operations are still being conducted by sea and air, Reuters reported.

"Wing leadership remains hopeful that we will safely rescue our pilot," an Air Force statement said, according to Reuters.

The Associated Press, Reuters, ANSA and LaPresse contributed to this report

U.S. Air Force / AFP - Getty Images

F-16 jet fighters taxi ahead of takeoff in Misawa Air Base in northern Japan in December. A U.S. military F-16 fighter jet from the base crashed into the sea off northern Japan on Sunday and its solo pilot was waiting for rescue at sea after ejecting, the coast guard said.

TOKYO -- A U.S. F-16 fighter jet crashed into the Pacific Ocean off the coast of northern Japan on Sunday and efforts were underway to rescue the pilot, a spokeswoman for the Misawa Air Base said.

The jet took off from the U.S. air base in Aomori and crashed about 11:30 Japan time (10:30 ET) some 200 miles northeast of Hokkaido, Japan's northernmost island, the spokesperson said.

"One person, the pilot, was on board. Efforts are currently underway to retrieve the pilot," she said, reading from a statement.

"The aircraft was en-route to North America when the incident occurred. The cause of the incident is unknown at this time."

The F-16 is made by Lockheed Martin Corp.

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