Searchers announced on Thursday they have discovered what they believe is the wreckage of Second World War ace Richard Bong’s plane in the South Pacific.

The Richard I Bong Veterans Historical Centre in Superior, Wisconsin, and the nonprofit Second World War historical preservation group Pacific Wrecks announced in March they were launching a joint search for the Lockheed P-38 Lightning fighter.

Captain Richard Bong nicknamed the plane “Marge” after his girlfriend, Marge Vattendahl.

Another pilot, Thomas Malone, was flying the plane in March 1944 over what is now known as Papua New Guinea when engine failure sent it into a spin. Mr Malone bailed out before the plane crashed in the jungle.

The expedition’s leader, Pacific Wrecks director Justin Taylan, said the search team discovered the wreckage in the jungles of Papua New Guinea’s Madang Province on May 15.

He released photos of himself in the jungle with chunks of metal on the ground. In one photo he points to what the caption calls a wing tip from the plane stamped with “993”, the last three numbers of the plane’s serial number.

Enlarging the photo shows markings that could be two “9s” but they are obscured by what might be dirt or rust. Another photo shows a piece of metal stamped with “Model P-38 JK”.

Mr Taylan said during a video news conference from Papua New Guinea on Thursday afternoon that the serial number and model identification prove the plane is Marge “definitely, beyond a doubt”.

“I think it’s safe to say mission accomplished,” Mr Taylan said. “Marge has been identified. It’s a great day for the centre, a great day for Pacific Wrecks, a great day for history.”

Mr Taylan has been researching the location of the crash site for years. He said that historical records suggested it went down on the grounds of a 150-year old plantation. Local residents initially showed the expedition the wreck of a Japanese fighter plane before telling the searchers about wreckage deeper in the jungle.

The explorers hiked through the jungle until they discovered wreckage in a ravine, Mr Taylan said.

At the top of the ravine they found two aircraft engines sticking out of the ground, indicating the plane went in nose-first and buried itself in the ground. Mr Taylan said Capt Bong painted the wing tips red and the paint was still on them.

Capt Bong, who grew up in Poplar, Wisconsin, is credited with shooting down 40 Japanese aircraft during the Second World War. He plastered a blow-up of Ms Vattendahl’s portrait on the nose of his plane, according to a Pacific Wrecks summary of the plane’s service.

Capt Bong shot down more planes than any other American pilot. General Douglas MacArthur awarded him the Medal of Honor, the US military’s highest decoration, in 1944. Mr Taylan said that Mr Bong shot down three planes while flying Marge.

Capt Bong and Ms Vattendahl eventually married in 1945. Mr Bong was assigned to duty as a test pilot in Burbank, California, after three combat tours in the South Pacific. He was killed on August 6, 1945, when a P-80 jet fighter he was testing crashed.

He died on the same day the United States dropped an atomic bomb on Hiroshima.

Ms Vattendahl was 21 at the time of Capt Bong’s death. She went on to become a model and a magazine publisher in Los Angeles. She died in September 2003.

A bridge connecting Superior and Duluth, Minnesota, is named after Capt Bong.

“The Bong family is very excited about this discovery,” James Bong, Richard Bong’s nephew, said in the news release. “It is amazing and incredible that ‘Marge’ has been found and identified.”