My guess would be that they intended this from the beginning, but that it sook some time to make the IT changes to support it.

I didn't see anyone post this already - here's an interesting interview from the WSJ with Frontier's CIO about all of the complex technical issues that they deal with, especially in light of the Bankrupcy and the recent fare structure changes:

http://online.wsj.com/article/SB123981031844421427.html