I was looking up something recently and stumbled upon this great article about the history of airport identifier codes. Things I learned were that early airports with two-letter weather station codes received an X on the end — LA became LAX and Portland's PD became PDX. And I finally found out why Newark is EWR. As it turns out, the Navy took all the N codes (surprised that the Marines didn't take all the M codes and Army didn't take the A codes!) which is why Newark does not start with N. The most intriguing to me is the Knoxville Airport. As it turns out it was built on land donated by the Tyson family in honor of their son who was killed in World War I and so the airport symbol is TYS. Want to learn more? Read HERE.