For the record, who is the world's largest operator of the world's most numerous airliner, the B737?
Old Smokey:
I remember reading somewhere, not too long ago that Southwest had some 480 '37s in service. Somewhere near 1/3 of them are said to be NGs with new ones arriving to replace the old at a good pace. I don't know if that makes them the largest, but that IS quite a few.
Best regards,
Westhawk