Originally Posted by
buckeyefanflyer
Regarding flight numbers for most airlines, westbound and southbound flight numbers were always odd numbers and eastbound and northbound flight numbers were even.
That has changed, not sure why.
Are you sure on your directions? Years ago I read that the airlines used the numbering system originally used on railroad timetables.
EZ to remember as a NW regular: "NW is odd"
Flights to north and west points odd numbers, flights south and east even.
NW was very good at following this convention on the TATL and TPAC routes. DTW-FRA was 52, FRA-DTW 51. DTW-NRT 11, NRT-DTW 12. Flight 1 took you to the orient, flight 2 brought you back.
This list of old NW and the new DL numbers seems to show DL following the NW pattern of odd and even flight numbers. North and west is still odd.