Originally Posted by
buddman
on my to be booked roster now is Baltimore dec 17-20 as well as SFO Jan 21-24.
Use Google Flights for easier searching of prices
LHR-BWI is GBP3839 if you go saturday to saturday 14 dec - 21 dec
LHR-SFO is GBP4130 if you tuesday to sunday 21 jan - 26 jan
Basically you are paying extra for going during the week. As Lucanesque said, adding a Saturday night gives you leisure travel prices as opposed to business prices. Booking more than 2 months in advance would also help.
