If you’re an observant visitor, you might have noticed that the American flag on the side of the Space Shuttle Discovery on display at our Steven F. Udvar Hazy Center appears to be backwards.

No, it’s not a very large (literally and figuratively) NASA snafu. The “backwards” flag is actually part of the US Flag Code, which applies to spacecraft, aircraft, and even service members’ uniform insignia.

According to United States Army regulations, “The full-color US flag cloth replica is worn so that the star field faces forward, or to the flag’s own right.” The flag must always be positioned to look like it is flying forward, so it’s really all about perspective.

Portrait of the prime crew of the Apollo 11 lunar landing mission. From left to right they are: Commander, Neil A. Armstrong, Command Module Pilot, Michael Collins, and Lunar Module Pilot, Edwin E. Aldrin Jr. On July 20th 1969 at 4:18 PM, EDT the Lunar Module "Eagle" landed in a region of the Moon called the Mare Tranquillitatis, also known as the Sea of Tranquillity. After securing his spacecraft, Armstrong radioed back to earth: "Houston, Tranquility Base here, the Eagle has landed". At 10:56 p.m. that same evening and witnessed by a worldwide television audience, Neil Armstrong stepped off the "Eagle's landing pad onto the lunar surface and said: "That's one small step for a man, one giant leap for mankind." He became the first human to set foot upon the Moon.

If you have the flag positioned on your left shoulder (as you can see on the Apollo astronaut’s spacesuits), then the flag appears as it would flying in the breeze on a flag pole—with the star field facing forward as the wearer moves forward. On other military uniforms, you’ll see what’s called the “reverse side flag” on the right sleeve.

Gen. Charles C. Campbell (left), commander of U.S. Army Forces Command, presents Maj. Gen. John A. Yingling with a U.S. flag. On the sleeve of Gen. Campbell's uniform you can see the reverse side flag.

This photo of the Space Shuttle Discovery and Enterprise shows the US Flag Code in action: On the side of Discovery, the flag appears as it would on a flagpole. On the side of Enterprise, you see the flag in reverse.

Space Shuttles Enterprise, left, and Discovery meet nose-to-nose at the beginning of a welcome ceremony at the Smithsonian National Air and Space Museum's Steven F. Udvar-Hazy Center, Thursday, April 19, 2012, in Chantilly, Va.

So, the next time you stop for a Space Shuttle selfie, take a second to explore both sides of Discovery to see how the flag positions change (and show off your flag code trivia!)