Here's the list (again)... as usual, recently added in italics!
US Domestic:
ABQ - Albuquerque, NM
ATL - Atlanta, GA
AUS - Austin, TX
BDL - Hartford, CT
BNA - Nashville, TN
BOS - Boston, MA
CAK - Akron/Canton, OH
CLE - Cleveland, OH
CLT - Charlotte, NC
COS - Colorado Springs, CO
CRP - Corpus Christi, TX
DAL - Dallas Love, TX
DCA - Washington, D.C. - Reagan
DEN - Denver International, CO
DFW - Dallas, Ft. Worth, TX
DIA - Denver Stapleton, CO
DTW - Detroit, MI
ELP - El Paso, TX
EWR - Newark, NJ
FLG - Flagstaff, AZ
IAD - Washington, D.C. - Dulles
IAH - Houston, TX
JFK - New York, NY
LAX - Los Angeles, CA
LGA - New York, NY
LIT - Little Rock, AR
MCO - Orlando, FL
MDW - Chicago Midway, IL
MGM - Montgomery, AL
MIA - Miami, FL
MSP - Minneapolis-St. Paul, MN
OKC - Oklahoma City, OK
ONT - Ontario, CA
ORD - Chicago O'Hare, IL
PDX - Portland, OR
PHL - Philadelphia, PA
PHX - Phoenix, AZ
PIT - Pittsburgh, PA
PVD - Providence, RI
RDU - Raleigh/Durham, NC
SAN - San Diego, CA
SAT - San Antonio, TX
SEA - Seattle, WA
SFO - San Francisco, CA
SLC - Salt Lake City, UT
STL - St. Louis, MO
TUL - Tulsa, OK
TUS - Tucson, AZ
XNA - Fayetteville, AR
International:
ARN - Stockholm, Sweden
CPH - Copenhagen, Denmark
FRA - Frankfurt, Germany
YQX - Gander, Canada