Two-character IATA-assigned code
that identifies a carrier
on arrival/departure signs, baggage
tags, Global Distribution System (GDS)
, tickets, etc. Usually it is an alpha
code (such as AI for Air India, EI for Air Lingus, and WN for Southwest Airlines) but sometimes it is alphanumeric
(such as F9 for Frontier Airlines, 7Z for Laker Airlines, and 5X United Parcel Service).