Join Date: Aug 2011
Location: Barcelona, London, on a plane
Programs: IB+ Gold, TK E+, Hyatt Globalist, Marriott LTP, IHG Diamond
Posts: 14,178
VS might offer much cheaper upgrades at the airport. Since SFO-LHR is a route with strong premium traffic, they don't want to fill J seats prematurely.
Much depends on whether Upper Class is empty and/or PE full - in which case VS will attempt to extract some added value before giving out free opups.