Hi there - we are struggling to find flights to SFO or SEA which are reasonably priced for our planned trip to the US departing around 21 September (well after Labor Day), returning around 9 October. We last travelled to the US around the same time in 2011, albeit to Boston, when our flights were £470 per person return. I did find flights for £550 about 3-4 weeks ago for our dates which seemed reasonably priced given the extra 2000 or miles or so, but by the time we had checked we could have time off with our respective employers, the cost had shot up to over £630 for the route we are looking to book now. Does anyone know why the costs may be so greatly increased? Is it down to fuel/taxes/new financial year? If anyone has any insight, I'd be very grateful to know.