Start applying RIGHT NOW, there is no value in waiting. I applied as a senior, was offered a slot a year post-graduation. The way things are going, you could bypass the regionals--UPT, bum in a unit flying all you can, hired at a major. If you don't get the slot, you'll still get a job at a regional. Applying now, shows your commitment is to the unit, not just getting a slot.

GF