Does JL use D and A inventory in the OW way? I haven't bothered to check since it doesn't affect me, but there is a good chance that part of joining OW for JL is to adjust there fare buckets. In which case you might not be able to book prior to JL starting its preparations. We know that JL cannot join prior to EI leaving (which is April 1), so that is the earliest possible date (and hopefully also the latest!). MA and RJ can join at any time. OW has never announced a date, other than "early 2007".