Originally Posted by
PAXboy
The reason they sit at LHR all day is the problem of the North/South route and only a one or two hour time change. European carriers mostly have no change of time zone and used to go out night and return day but as the Biz traffic increased, Biz did not want to waste a day and tourists neither. Consequently everyone pays for the 12 hours (or so) of parking time.
While this is likely correct, I have always wondered why there were so few late afternoon (or early evening) flights from Europe to the U.S.