I am planning to head to Berlin the third week of April (2019) via London preferably on AA50, but I am of course flexible on this to clear my upgrade. My schedule is flexible enough I can fly out any day Sunday-Tuesday. Is there a day typically better for loads to be able to clear? I am used to flying the JFK-LHR route, and have not missed an upgrade yet, so just curious about this route with less frequency. I would be looking for an upgrade from Y to J.