Blonde,
You may want to try the AA thread.
Go to AA.com
on the specials box you ca put in city pairs to see what's what.
I think you can find some good deals.
Good Luck.
I'd look at PHL-JFK-LHR and back. See what that cost - lots of miles.
Also PHL-JFK-MIA-LHR and back.
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TANSTAAFL - but if you work it right, FF miles comes pretty close.