Spirit Airlines
Frontier Airlines is the only airline to fly out of Wilmington-Philadelphia Regional Airport.
The airlines that fly to Sacramento (Sacramento International Airport SMF) in North America, USA include Alaska Airlines, American Airlines, Horizon Airlines, Jet Blue Airlines, and many more smaller airlines.
Southwest Airlines Flies out / into Terminal 3
"Skywest is technically an international flight company as they do fly internationally. However, they only have a few international destinations they fly to."
Yes they are, they don't fly international
Domestic Airlines fly nationally (inside one country, such as New York City to Denver) and International Airlines fly internationally (from one country to a different one, often times overseas, such as New York City, USA to Frankfurt, Germany).
Many different airlines fly into the Baltimore/Washington International airport. A few of them include: Air Canada, AirTran, American Airlines, British Airways and Condor.
terminal 2
British Air does not fly into Nashville. Nashville International Airport (BNA) is serviced by Air Canada, Alaska Airlines, American Airlines, Contour Airlines, Delta, Frontier Airlines, Jet Blue, Southwest Airlines, and United.
Alaska Airlines has three major airport hubs at Seattle-Tacoma International, Ted Stevens Anchorage International, and Portland International. On Alaska Airlines, you can fly directly to airports in the USA, Canada, and some in Mexico.
American AirlinesSouthwest AirlinesDelta AirlinesUnited Airlines