I am looking to fly from JER to LON and then on to DFW on 27 March and coming back to London 1 Oct.

My problem is that I would like to fly BA not AA on the route, but my JER flight does not get me into LON early enough to get to LHR.

So I thought I would do a multi-trip itinerary/stopover using the BA tool, but it comes up a lot more expensive. JER-LON-DFW with AA comes up at £585 but if I do it with the tool, it comes up at £800+, which is ridiculous!!

Is it actually possible to get cheap oneway tickets to the US, as well?