There are two cases I know of where an airpower intervention was able to win/prevent a conflict by itself: Kosovo and Iraq between the Gulf Wars. But I don't think those are good models for what's going on in Libya right now.
In both those cases, you had an ethnic group looking to break off a chunk of the country for their own, not to topple the current regime. There was an equilibrium at the end: Milosevic/Hussein accepting the loss but staying in power, the Kosovars/Kurds enjoying their autonomy, NATO/UN maintaining a status quo. Even then, it took a shit ton of bombing to get Serbia to back down, and Saddam still kept trying to mess with Kurdistan.
Libya, though? The opposition forces are a loosely defined group that seems to exist solely to depose Qaddafi, mostly based in the east but with no major cultural or geographic divide from the rest of the country, and no reason to accept a territorial split. Likewise, no reason to think Qaddafi would be okay ceding half his country to forces dedicated to his downfall.
From where I sit (and right now I'm totally Guy On Internet Talking Like He Knows Shit) it looks like a war that goes until someone crushes the other side, where the fundamental conflict prevents a truce. Which means France/Britain/USA need to start thinking really goddamn hard about how far they're willing to go with this.