Is it in how well one recites the Pledge of Allegiance?

In whether the American flag is permanently attached to the siding of one's home?

Or in how close to perfect your attendance has been for each and every election (yes, even the local fire district's)?

Service to country has been a reliable yardstick for centuries, military service in particular.

By that standard, Philadelphia's streets this weekend will be walked by some convention attendees who are among the most patriotic Americans this country has known.

They're the Tuskegee Airmen, the remaining coterie of those World War II pilots, navigators, bombardiers, gunners, mechanics and related personnel who fought for a country they loved that didn't always love them back. Why? Because their skins are black.

It wasn't a new phenomenon. African Americans have fought for the United States since even before there officially was one. And from the Revolutionary War to the Civil War to the one against Hitler's axis, black soldiers' and sailors' consistent reward was a segregated society that dismissed their patriotism.

Just ask the Tuskegee Airmen.

President Franklin Roosevelt, anticipating U.S. entry into Europe's war, began a program to train civilians to become military pilots in 1938. In 1940, Tuskegee Institute, the black college founded by Booker T. Washington in 1881, was selected to be part of the program.

That in itself was an amazing achievement. The white military hierarchy in earlier wars had questioned blacks' bravery only to see them prove their heroism again and again in battle. This time, African Americans were said to lack the intelligence to fly a plane.

Again, the naysayers were proven wrong. The black cadets learned their lessons well and became the Army Air Corp's 99th Pursuit Squadron. Under the leadership of Capt. Benjamin O. Davis Jr., a second unit was formed, the 332d Fighter Group, which absorbed the 99th.

The black pilots flew P-39s and P-40s, then mightier P-47s, and finally sleek P-51 Mustangs. The Tuskegee Airmen's first overseas deployment was to North Africa in 1943. They saw their first combat later that year, flying over Italy.

According to the U.S. Air Force, from June 1944 to the end of the war, the 332d flew 200 bomber escort missions, shot down 111 enemy aircraft, destroyed 150 more on the ground, knocked out more than 600 railroad cars, and sank one destroyer and 40 boats and barges.

The airmen's losses - 150 dead.

In addition to the 332d, Tuskegee Airmen also formed the 477th Medium Bombardment Group. In all, Tuskegee trained 992 pilots and sent 450 overseas during the war. Their service helped spur President Harry Truman to order the desegregation of all U.S. armed forces in 1948.

It would take years to have a similar order apply to their civilian lives. Like past black veterans, they returned to a land of bias and racial hatred. But it's not too late to show appreciation for a job well done.

The Tuskegee Airmen are holding their 37th annual convention at the Philadelphia Marriott Downtown this weekend. If you get a chance to meet one, find an appropriate way to express your gratitude to these true patriots who wouldn't let prejudice stand in the way of service to their country.