Here's an interesting topic- What is the origination of some 3-letter airport codes that appear to have more to it than just the city name? I know some of these, but not most:

GEG Spokane
MSY New Orleans
IAD Washington-Dulles
MCO Orlando
MCI Kansas City
BNA Nashville
ORD Chicago-O'Hare
EZE Buenos Aires
OGG Kahului
SDF Louisville
BDL Hartford
FCO Rome
GRU Sao Paulo
RSW Ft. Myers
MDT Harrisburg

and who banished all Canadian cities to have codes starting with Y?