| Airline | Image | IATA | ICAO | Callsign | Primary hubs, secondary hubs | Founded | Notes |
|---|
| Alaska Air Group | | AS | ASA | ALASKA | Seattle/Tacoma Daniel K. Inouye International Airport Anchorage Los Angeles Portland (OR) San Diego San Francisco | 1932 | Founded as McGee Airways and commenced operations in 1944 as Alaska Airlines. Hawaiian Airlines merged into Alaska Air Group in 2024, though the two airlines remain as separately branded. |
| Allegiant Air | | G4 | AAY | ALLEGIANT | Las Vegas Allentown Appleton Asheville Bellingham Cincinnati Destin/Fort Walton Beach Des Moines Flint Fort Lauderdale Grand Rapids Indianapolis Knoxville Nashville Orlando/Sanford Phoenix/Mesa Pittsburgh Provo Punta Gorda Sarasota Savannah St. Petersburg/Clearwater | 1997 | Founded as WestJet Express and began operations in 1998 as Allegiant Air. |
| American Airlines | | AA | AAL | AMERICAN | Charlotte Chicago–O'Hare Dallas/Fort Worth Miami Philadelphia Phoenix–Sky Harbor Los Angeles New York–JFK New York–LaGuardia Washington–National | 1926 | Founded as American Airways and commenced operations in 1936 as American Air Lines Largest airline in the world based on airline company revenue, and scheduled passenger miles flown (per year) in 2025. |
| Avelo Airlines | | XP | VXP | AVELO | New Haven Charlotte/Concord Lakeland Raleigh/Durham Wilmington (DE) Wilmington (NC) | 1987 | Founded as Casino Express Airlines and commenced operations in 1989. Started scheduled service in Burbank, CA, April 28, 2021. |
| Breeze Airways | | MX | MXY | MOXY | Charleston (SC) Akron/Canton Fort Myers Hartford New Orleans Norfolk Orlando Providence Provo Raleigh/Durham (begins Q1 2026) Tampa Vero Beach | 2018 | Founded as Moxy Airways, but was renamed due to trademark issues. |
| Delta Air Lines | | DL | DAL | DELTA | Atlanta Detroit Minneapolis/St. Paul New York–JFK Salt Lake City Boston Los Angeles New York–LaGuardia Seattle/Tacoma | 1924 | Founded as Huff Daland Dusters and commenced operations in 1929 as Delta Air Service. |
| Frontier Airlines | | F9 | FFT | FRONTIER FLIGHT | Denver Atlanta Chicago–O'Hare Cincinnati Cleveland Las Vegas Miami Orlando Philadelphia | 1994 | |
| JetBlue | | B6 | JBU | JETBLUE | New York–JFK Boston Los Angeles Fort Lauderdale Orlando | 1998 | Founded as New Air and commenced operations in 2000 as JetBlue Airways. |
| Southwest Airlines | | WN | SWA | SOUTHWEST | Dallas–Love Atlanta Baltimore Chicago–Midway Denver Houston–Hobby Las Vegas Los Angeles Oakland Orlando Phoenix–Sky Harbor Nashville | 1967 | Founded as Air Southwest and commenced operations in 1971 as Southwest Airlines; largest airline in the world based on number of passengers served per year. |
| Spirit Airlines | | NK | NKS | SPIRIT WINGS | Fort Lauderdale Atlantic City Atlanta Detroit Las Vegas Chicago–O'Hare Dallas/Fort Worth Baltimore Orlando Houston–Intercontinental | 1980 | Founded as Charter One. |
| Sun Country Airlines | | SY | SCX | SUN COUNTRY | Minneapolis/St. Paul Dallas/Fort Worth Las Vegas | 1982 | Commenced operations in 1983. Operates some Amazon Air cargo flights. |
| United Airlines | | UA | UAL | UNITED | Chicago–O'Hare Denver Houston–Intercontinental Newark San Francisco Washington–Dulles Guam Los Angeles | 1926 | Founded as Varney Air Lines and commenced operations in 1931 as United Air Lines. |