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.

[UPDATE: A D-Day Plane Is Flying Again; With Photos]

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.

From Normandy to Oshkosh

At the Air Force Historical Research Agency in Montgomery, Ala., Matt Scales, then a member of the Air National Guard, was researching John M. Donalson, who piloted the plane on the day it soared over the beaches of Normandy.