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Join Date: Apr 2012
Location: Leeds, UK
Programs: BA GGL/CCR, GfL, HH Diamond
Posts: 42,996
Aha, 6 July, thanks for adding it. So this is what EF says for that date for the two AA direct flights:
AA 736 - 06/07/17 7:15 PM
J3 R0 D0 I0 Y7 B0 H7 K7 M7 L7 G7 V7 S7 N7 Q7 O7
AA 728 - 8:40 PM LHR
J2 R0 D0 I0 Y7 B0 H7 K7 M7 L7 G7 V7 S7 N7 Q7 O7
So it seems there is some limited space on the AA flights still. Also as noted by nufnuf77 there are lots of possibilities if you are willing to add a connection from PHL to somewhere else before the TATL.
If not though and BA are not booking you on to AA that day you would go a different day as noted. If you went for the Y flight I am not sure about EC261 and whether it applies - you do seem to have options which don't involve a downgrade though.