DL doesn't participate with EF on showing award/upgrade inventory availability. DL changed GUC upgrade availability recently when they made it good for only a one-class upgrade and now only requires Z class availability which is a revenue class (and not an award/upgrade class). EF shows revenue fare class availability on any airline (including AA). As noted above, if you are looking for GUC upgrade eligibility on AF operated flights, you will need to look at AF coded Z availability (and not DL coded Z availability).