And why do some airlines have the return flight no as one higher than the outward, and some one lower?
e.g.
EK9 DXB-LGW
EK10 LGW-DXB (return of same aircraft)
SQ52 SIN-MAN
SQ51 MAN-SIN
Not sure of the reason but LH used to and possibly still have even numbered flights from Germany and odd numbered flights to Germany. Can't remember what happened on domestic routes though.