I just looked at October 24, 2020 with the following legs:
Eastbound ICN DTW....(DL158) flight time is stated as 12:55 (hh:mm - using Deltas scheduled times) on an Airbus A350-900
Westbound DTW ICN...(DL159) flight time is stated as 13:40 (hh:mm - using Deltas scheduled times) on an Airbus A350-900
.......almost 1 hour difference flight time (well 45 minutes)....why?....what is the only other differences besides direction?

When Concorde was still flying, I think you would have found JFK to LHR flight time leg was less than the LHR to JFK flight time leg.

Please help me think more outside of the box if I'm missing something else - I will keep my thinking open and blinders off. Thanks