Originally Posted by
cmd320
That’s all about the prevailing upper-level winds. As a general rule, in the northern hemisphere, upper-level winds flow west to east. Therefore an eastbound transatlantic flight from JFK to LHR will almost always be shorter based on time than the westbound LHR-JFK equivalent. This is amplified in the winter season when upper level winds are stronger than they are in the summer season. In winter months JFK-LHR flights on subsonic aircraft have been recorded under five hours whereas westbound flights may take 8 hours or more. This is entirely based on the winds enroute. The actual distance between the two destinations always remains the same.
Thanks for the additional information, jet streams will greatly determine speed as well as time of a specific flight. So, then I can also state another fact that an eastbound flight will use less fuel than a westbound flight using the same pairs of cities - and therefore this also becomes another reason that Delta is using CPT to return to ATL and not JNB. Thanks again.