Booked a flight for WAAAY in advance (March! Don't get away much, sadly...) with BA - 0117 LHR>JFK on a Saturday. Times are:

LHR 0830 JFK 1200

Those times are fine, yet I notice that on BA's timetable, 0117 has these times ONLY Wed-Sat. The same route Sun-Tues has these times:

LHR 0820 JFK 1105

Same plane (747) listed for each types.

Why would departing 10 minutes earlier cut the flight time down by 55 minutes? Surely BA cannot be adding 45 minutes of padding time for half of the week?!

(Also if anyone could reassure me that we won't be stuck for hours at JFK T7 immigration, that would be wonderful. JFK's immigration times seem all over the place. We have another flight to catch from T8 3 hours later and I had assumed this would be PLENTY of time - yet now it appears perhaps not...)