There is no explicit way to do it. Are you looking for ideas on how to track down the business/first seats using the web site? Because the short answer is (one that lots of FTers probably already know, so no offense if this sounds like I'm Captain Obvious): narrow the search as much as possible, to keep Alaska flights out of the results. So search one direction at a time, starting with the long-haul (SFO/LAX-CDG if you're flying AF, for example). Then work backwards to your origin point to add the Alaska flights. It's slow, but it usually works.