So who volunteers to give up their capacity so that others can benefit? you?
Same thing has happened in Australia with Qantas and Virgin (and a few other minor carriers) oversupplying seats, but neither will back down and they are not allowed to by law 'work out any deals'
Both posted big yearly losses (Qantas its biggest in its history) so the only thing that made them back down was that both do not have access to deep enough pockets to 'force the other out' by over-supply
The game will go the same way, some airlines will sustain losses that lead them into bankruptcy or they will close unprofitable routes, so the market ends up working itself out