Available through March. Weekend (Fri-Sun) runs possible with little (or no) premium. (Although, this being one of the "most funest" destinations I have been to, I recommend you stay at least a couple of days.)

Pay attention to your connection to the BA flight in LON. I've only seen the lowest fares with the LGW-RAK-LGW routing. The non-stop routing through LHR is more, and it doesn't run every day.

If you can't see the low fares, change your departure and/or return by one day. For consistency, I used Wed-Wed pricing in my examples below.

Prices from aa.com: (Note: some examples may show pricing for a LHR // LGW connection. I don't have time to resolve this issue for every example. I'll leave that detail to you. )

NYC, $385+
SFO/OAK/SJC, $421+
BOS, $422+
ORD, $433+
STL/IAH, $436+
DFW, $441+
LAX, $447+
SDF, $473+
PHX, $487+