I agree with nu, lack of fences is a plus and a big operational bonus.
As red guys retired, green guys were able to get into red seats due to insufficent bidders. So a junior red guy never got senior but he did have earlier access to higher paying equipment. A young red friend of mine called it "running in front of the green wave". You could never be senior, so you might as well go make money.
Another point to add is ALL seats on the airline were coded red/green. The only way a new hire held anything was insufficent bidders. That is why us blue guys only had recall rights with each other, no seat was blue.
Confused yet........don't worry, it don't matter no more!
Ferd