Originally Posted by jrl767

in general, the biggest risk is having your London-ARN (which is the actual code for Stockholm) leg on a different ticket (or, worse, a different airline, in the interest of saving a few dollars) from ARN-SFO: if you're delayed out of London to where you'll miss the departure for home, the originating airline has no responsibility to get you anywhere other than ARN, and once you get there, SAS has no responsibility to reaccommodate you unless you buy a walk-up fare

a better option might be to look at an open-jaw (SFO-ARN and LHR-SFO); in this case, the one-way from ARN to London can easily be on a stand-alone ticket or a different airline