Kaitak From Ireland, joined Aug 1999, 12166 posts, RR: 35 Reply 3, posted (14 years 3 months 3 weeks 4 days 9 hours ago) and read 551 times:
Clipper is quite correct; each airline is given its own identifier. Pan Am was -21 and it ran through all the numbers, then letters and numbers (e.g. Thai, -D7), then numbers and letters (e.g. -8E, Asiana) and more recently, two letters. This is actually very useful in identifying the first operator of an aircraft, as it will carry this code through its life; e.g. a few of the Olympic 747s were -212s, which identifies them as being ex-Singapore Airlines.
As to options and engines, this doesn't actually have a bearing on the number. For example, JAL was always a PW user until it got its -400s, but still kept its -46 identifier.
DC-10 From , joined Dec 1969, posts, RR: Reply 4, posted (14 years 3 months 3 weeks 4 days 8 hours ago) and read 544 times:
It's boeings customer code....Like a 747-212B means it's a 747-200B 12 is for Singapore airlines. This number will follow the aircraft no matter what airline ends up with it. Pan Am bought several of SIA's -200s and they remained 212's in Pan Am's fleet record.