Britannia Airways 737-200s.
Which of these aircraft were the early basic version and which were the Advanced ? My guess would be:
AVRL, AVRM, AVRN, AVRO, AXNA, AXNB, AXNC, AWSY and AZNZ - all early models.
Then, everything from BADP to BKHF plus BGNW and BJXJ were the Advanced variant.
I don't know about the various leased specimens from Gulf Air, PLUNA etc.
Thankyou.