JL is changing a lot of their fare codes, as part of joining OW. About a dozen have to change (for example JL uses A as a sold economy code, when on OW it is discounted F). I think, but don't know for sure, that JL is converting to the OW standard award codes (which are U for J and Z for F). But that might not go into effect until April 1. The answer to your question probably varies by date.