Color: Bright red attracts attention. The DC-4 symbolizes reliability and speed of transport.
The 1946 airmail stamp featured the venerable DC-4 Skymaster. The DC-4 at the time was a symbol of reliability and speed. The impressive red color alerted postal sort clerks that the letter is airmail and needed to be transported to the nearest airport mail facility.
This stamp heralded one of the most sweeping rate reductions in U.S. Air Mail history. For many letters this reflected a three cent reduction, but for the Territories of the United States, including Alaska and Hawaii the reduction was much greater. This was doubly critical, since mail to the territories took weeks to arrive unless sent via air.
According to Glass, in some cases this reduction was from as much as 90¢ an ounce!
For more information about this stamp and other U.S. airmail stamps
go to: http://www.livefromsiliconvalley.com/airmail/
Here is a little video of the DC-4E