Wirelessly posted (BlackBerry: BlackBerry8530/5.0.0.1030 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/417)
It's also possible to fly SEA-JFK-LHR on AA metal.
And YVR-JFK on CX, connecting to JFK-LHR on AA. But you would have to book each of those legs as a separate redemption, in order to avoid BA's multi-partner redemption rate.