List of all airlines that serve retail passengers in the U.S.?

Answer 1

When you include the regional and commuter airlines, there are dozens. Do you want just domestic or add the couple of dozen international airlines?
For example, here are over 20 that serve SeaTac (Seattle Tacoma) airport and this does not include 2 float plane lines that serve Seattle and Victoria from the downtown lake.
Air Canada (including Air Canada regional airlines)
800 247-2262 North Satellite 15
Alaska Airlines
800 426-0333 Concourse C, Concourse D 13, 14
America West Airlines
800 235-9292 Concourse A 9
American Airlines
800 433-7300 Concourse A 2
Asiana Airlines
800 227-4262 South Satellite 1
British Airways
800 247-9297 South Satellite 1
Charter Airlines South Satellite, Concourse B, Concourse C 5, 6
China Airlines
800 227-5118
Departs Concourse A;
Arrives South Satellite
1
Continental Airlines
800 525-0280 Concourse B 9
Delta Air Lines
800 221-1212 Concourse A 3, 4
EVA Air
800 695-1188 South Satellite 1
Frontier Airlines
800 432-1359 Concourse A 6, 7
Hawaiian Airlines
800 367-5320 Concourse B 5
Horizon Air
800 547-9308 Concourse B, Concourse C, South Satellite 12
JetBlue Airways
1-800-JETBLUE Concourse A 6
KLM Royal Dutch Airlines See Northwest Airlines
Korean Air
1- 800-438-5000,
[phone]
South Satellite 1
Northwest Airlines
800 225-2525 South Satellite 8
Scandinavian Airlines
800 221-2350 South Satellite 1
Southwest Airlines
800 435-9792 Concourse B 11
Sun Country Airlines
800 359-6786 Concourse A
3, 4
United Airlines (including United Express)
800 241-6522 North Satellite 15,16
US Airways
800 428-4322