<p>It stands for Red Tag Bastard. Here's wikipedia's version:</p>
<p>Red Tag Bastards - A nickname for some class years at the United States Air Force Academy. Each class year is assigned one of the four rotating colors (gold, blue, silver, and red, in that order) to identify it. The new incoming class is assigned the color of the last graduating class. The "tag" term comes from the fact that the class colors are used on the name tags outside of cadets' rooms. RTBs are those classes assigned red as their class color. The class of 1962 was the first "red tag" class at the Academy; the incoming Class of 2010 will be the next one. </p>
<p>And if I remember correctly it has something to do with General Spaatz..</p>