World War II was immense. So many numbers boggle the mind. Every day from Sept. 1, 1939-Aug. 14, 1945, 27,000 people were killed. That’s nine 9/11s every day for six years. Nearly 14 million Americans served during the war, the U.S. manufactured 300,000 airplanes. Even narrowing the focus, the numbers still amaze.

Three of every four German submariners died. The Soviets killed more of their own soldiers than total U.S. combat deaths. Even those who have studied the war for years cannot help but be stunned by such figures and many, many more.

But even more than 70 years on, there are still relatively unexplored areas of the war whose numbers are also quite astonishing. So it is with the number of Americans killed during aircrew training. The number of pilots and crew that died in training accidents in the U.S. during the war is 10 times the number of American deaths on D-Day. The heroism of those that stormed the Normandy beaches has been celebrated in countless books and movies.