I found something strange in the succession of serial-numbers from Boeing aircraft. Why are, in the same fleet, higher (later) numbers used on older aircraft while newer aircraft carry lower numbers?
Just one example of this are
9V-SFA (1994): serial-no. 26563
9V-SFB (1994): 26561
9V-SFC (1995): 26560
9V-SFD (1995): 26553
9V-SFE (1996): 28263
9V-SFF (1997): 28026
9V-SFG (1998): 26558
9V-SFJ (2001): 26559
Very odd is that SFE and SFF seem to be from a later order as the serial-no is much higher (by more than 1500 frames) and the later built SFG and SFJ have low numbers again, SFJ even a number lower than SFA built 6 years earlier. What is the sense behind that?
I noticed the same with Korean Airs 744s, while LHs 744s serial-numbers are linear with age.