I was finishing a P- 51 and I noticed that the earlier planes did not have the bars with the stars. After the second world war all the american korean fighters had the bars. What was the signifance of not having the bars earlier and then adding them later? I have not seen a jet without them.
Curious,
Burt

Take a look here:
http://www.airpowermuseum.org/trinsign.html

It doesn't tell about the red bar, but I would assume that was added when the Air Force became it's own branch of the military in 1947.

Actually, this link seems to confirm my theory:
http://www.aircraftspruce.com/catalo...starsnbars.php

Military paint schemes, camouflage, markings, and insignia are called out in various Specs and Technical Orders (TOs).

Spec. AN-I-9b covers the national insignia - amendment 2 was issued in January 1947 adding the red stripe.

Don't have the actual reason why but it is generally believed that this was to bring back all the colors of the US flag (Red was deleted in '41 to avoid confusion with enemy markings - red dot in the white star and red surrounding border).

Craig