Are Oktoberfest beers available in Germany before the official start of the festival? In the US where I live, fall brings beers labelled "Oktoberfest", usually Bavarian Märzenbiers.  I like this style and look forward to it.

This year it happens that I'm going to be passing through Munich a few days before the start of their Oktoberfest.  It'd be great to be able to sample Oktoberfest beers fresh out of the tap where they're made, rather than waiting for whatever makes it across the Atlantic to me later.  Am I likely to find any Oktoberfest beers in the Munich airport in the week before the festival, or is that date the "debut" and I'll just have to settle for other German beers when I'm there?
I'm not sure if you will find any Oktoberfest beer at the airport but they are available several weeks before "official" start in big groceries or beer shops.  Hacker-Pschorr Oktoberfest Märzen, Paulaner Oktoberfest and Löwenbräu Oktoberfestbier were already available three weeks  ago even in nothern Germany.