It took two eagle-eyed historians to track down the plane that led hundreds of Allied aircraft into Normandy during World War II.

A few years ago, the historical treasure was languishing in an aircraft bone yard in Wisconsin.

The plane, a twin-engine C-47 called “That’s All, Brother,” carried American paratroopers into German-occupied France on June 6, 1944, or D-Day. It led the main formation that dropped thousands of men into what became a bloody but decisive battle, paving the way for the liberation of northern France from the Nazis.

Like many other World War II planes, “That’s All, Brother” was sold for private use after the fighting ended. It cycled through a series of owners and its historical significance was in danger of being forgotten.

But in 2007, the two historians started following a paper trail.