Every airline is different. I have one friend who interviewed w/SWA, got hired, and even got called for a class before he ever put his retirement paperwork in. His availability was whenever he wanted.

Another friend got w/in one month of retirement before getting the interview call from UPS. He interviewed, and was called for a training class about 2 1/2 weeks after his interview. All w/in a span of about 2 months.

Both very extreme examples. Personally, I started 10 months out, and am wishing I had added a couple of extra months to my planning. I'm still about 4-5 classes down in the SWA pool.