A jagged scrap of riveted aluminum might be the best evidence yet that Amelia Earhart's attempted flight around the world ended at a remote Pacific Island.

Contrary to reports, however, it's premature to call the case closed.

The panel, found years ago on an atoll known as Nikumaroro, is an excellent match for a window patch on Earhart's Lockheed Electra, according to new research.

But Ric Gillespie stops short of calling it conclusive proof.

He heads the International Group for Historic Aircraft Recovery (TIGHAR), a Chester County-based network of experts and enthusiasts who have made 10 trips for 25 years to Nikumaroro.

"We reached a point where we feel very confident we have a part of the airplane," he said by phone this morning from his home in Oxford, west of Kennett Square.

But, he added, "I don't think this is going to be what we call the 'any-idiot artifact' that solves the Earhart mystery."

On a scale of 1 to 10, Gillespie's confidence is at 9.8, he hesitantly told NBC's Today show. More major media appearances were scheduled, including Anderson Cooper's show tonight on CNN.

Finding proof could happen soon, with a June expedition planned.

A strange sonar pattern discovered two years ago could mark the underwater resting place of Earhart's Lockheed Electra, and TIGHAR will use divers to hunt for wreckage and a remote-operated vehicle to try to photograph the fuselage.

"We need to get back there and look at that anomaly," Gillespie said. "...It's the right length and the right height, and we know it's in the right place to be the airplane."

Nearby parts of the island will also be searched for signs of an early campsite.

Over the years, TIGHAR has amassed a remarkable array of artifacts and fact-based arguments.

The prevailing theory about the 1937 disappearance was that Earhart and navigator Fred Noonan went down in the Pacific while heading for Howland Island, their stop before Hawaii on the way to the finish line in Los Angeles.

TIGHAR's theory is that the pair mistakenly believed they'd flown north of Howland and turned south. Running out of fuel, they landed on the reef off Gardner Island, as Nikumaroro was then called.

Radio buffs, however, reported picking up transmissions. A Florida girl took notes, detailing how Earhart identified herself and repeated something that sounded like "New York City."

A freighter called the Norwich City was abandoned at Nikumaroro in 1929. If Earhart was there, she certainly would have seen it.

A photograph taken in 1938 shows an object sticking out of nearby water – perhaps a plane's wheel assembly.

That same year, the island became inhabited by other islanders. Years later, at least five of them told of finding a wrecked airplane in the surf and salvaging scraps, according to Gillespie.

One woman marked a map to show the spot.

It was near the location of the sonar anomaly.

Physical evidence found during expeditions: a woman's shoe, a sextant box, a zipper piece, a broken pocket knife, a chunk of rouge, a shard of a cosmetics jar -- all consistent with Earhart and her belongings, according to TIGHAR – as well as small remnants of plexiglas and other materials that could have come from her plane.

A set of 13 bones found on the island was lost after being analyzed in 1940 by a British doctor. A forensic anthropologist who checked his detailed measurements concluded the bones belonged to a woman of European descent.

Fascinating. Compelling. Not quite definitive proof.

The metal scrap is the best evidence yet, Gillespie believes.

His wife, Patricia Thrasher, was taking photographs inland during a 1991 expedition, when he heard her call out, "You might want to come over and look at this."

There it was, a piece of aluminum about two feet wide and a foot and a half tall, with five lines of rivet holes, tears, scrapes and even a bit of coral growth, which shows the metal had been submerged.

At first, Gillespie concluded it must been used to repair a section on the bottom of the Electra.

"The conclusion is inescapable. This is a piece of Amelia Earhart's aircraft," he wrote in 1992.

Skeptics soon changed his mind, and for more than two decades, the scrap remained a mystery.

About four months ago, a researcher wondered about a patch installed over a rear window during Earhart's stop in Miami.

It might explain why the riveted piece matched no known section of any plane.

The ad hoc patch covered a customized navigational window that was unique to Earhart's Electra.

The size, known from photographs, was right. The number of rows of rivets seemed right, according to photo analysis by forensic imaging specialist Jeff Glickman.

Earlier this month, Gillespie, Glickman and other experts visited an Electra being restored in Kansas to help determine what the repair must have looked like.

The patch had to have horizontal "stiffeners" or reinforcing metal strips to keep the panel from warping, they concluded.

The artifact's rivet lines correspond to a reasonable pattern for such stiffeners.

"Let's say we found nothing more," Gillespie said. "This thing just showed and we happened to pick this up. ... You'd still say, well, it's a part of her airplane."

This piece still has more to teach, he's convinced.

The fact that no other wreckage scraps were found on the island suggests the Electra may not have broken into bits.

"Maybe the airplane is much more intact than we dared to think it was," Gillespie said.

An expensive expedition using minisubs was scheduled for last month but was canceled when fund-raising fell short.

The next expedition, a much more targeted affair, has fewer financial worries, Gillespie said.

Instead of a large research vessel from Hawaii, the plan calls for a less pricey dive boat out of Fiji, cutting round-trip travel time by a week.

Gillespie's still anxious.

"There are no guarantees of success, and that makes it tough," he said. "But no guts, no glory."

Contact staff writer Peter Mucha at 215-854-4342 or pmucha@phillynews.com. Follow @petemucha on Twitter.