| BOS–DCA | Boston – Washington | 1,176 |
| BOS–ORD | Boston – Chicago | 1,101 |
| DFW–ORD | Dallas-Fort Worth – Chicago | 1,041 |
| PHX–SEA | Phoenix – Seattle | 925 |
| DEN–ORD | Denver – Chicago | 824 |
| ATL–DCA | Atlanta – Washington | 811 |
| BNA–ORD | Nashville – Chicago | 731 |
| DTW–ORD | Detroit – Chicago | 727 |
| MSP–ORD | Minneapolis – Chicago | 710 |
| CMH–ORD | Columbus – Chicago | 673 |
| DFW–MIA | Dallas-Fort Worth – Miami | 662 |
| DFW–PHX | Dallas-Fort Worth – Phoenix | 649 |
| BNA–DCA | Nashville – Washington | 642 |
| CVG–ORD | Cincinnati / Covington – Chicago | 628 |
| MCI–ORD | Kansas City – Chicago | 625 |
| ORD–TVC | Chicago – Traverse City | 616 |
| ORD–XNA | Chicago – Fayetteville/Springdale/Rogers | 544 |
| ORD–STL | Chicago – St Louis | 539 |
| MKE–ORD | Milwaukee – Chicago | 534 |
| OKC–ORD | Oklahoma City – Chicago | 515 |
| MEM–ORD | Memphis – Chicago | 514 |
| CLE–ORD | Cleveland – Chicago | 512 |
| MSN–ORD | Madison – Chicago | 504 |
| AUS–DFW | Austin – Dallas-Fort Worth | 486 |
| GRR–ORD | Grand Rapids – Chicago | 483 |
| GRB–ORD | Green Bay – Chicago | 483 |
| DFW–SAT | Dallas-Fort Worth – San Antonio | 479 |
| ORD–TUL | Chicago – Tulsa | 479 |
| ORD–SGF | Chicago – Springfield | 471 |
| DFW–SGF | Dallas-Fort Worth – Springfield | 470 |
| OMA–ORD | Omaha – Chicago | 468 |
| DFW–MAF | Dallas-Fort Worth – Midland | 462 |
| ORD–RIC | Chicago – Richmond | 456 |
| ICT–ORD | Wichita – Chicago | 447 |
| MIA–SJU | Miami – San Juan | 446 |
| ORD–SDF | Chicago – Louisville | 446 |
| CLT–MIA | Charlotte – Miami | 440 |
| FAR–ORD | Fargo – Chicago | 439 |
| ORD–YUL | Chicago – Montréal | 434 |
| DFW–DTW | Dallas-Fort Worth – Detroit | 433 |
| ORD–TYS | Chicago – Knoxville/Maryville | 425 |
| DFW–SLC | Dallas-Fort Worth – Salt Lake City | 422 |
| BOS–BUF | Boston – Buffalo | 418 |
| DFW–XNA | Dallas-Fort Worth – Fayetteville/Springdale/Rogers | 412 |
| BWI–ORD | Baltimore – Chicago | 404 |
| BOS–CVG | Boston – Cincinnati / Covington | 404 |
| FSD–ORD | Sioux Falls – Chicago | 402 |
| LIT–ORD | Little Rock – Chicago | 401 |
| IAH–OKC | Houston – Oklahoma City | 399 |
| DFW–FLL | Dallas-Fort Worth – Fort Lauderdale | 397 |
| GSP–ORD | Greenville/Greer/Spartanburg – Chicago | 395 |
| DFW–SDF | Dallas-Fort Worth – Louisville | 394 |
| DSM–ORD | Des Moines – Chicago | 392 |
| DFW–LIT | Dallas-Fort Worth – Little Rock | 390 |
| GSO–ORD | Greensboro – Chicago | 388 |
| CID–ORD | Cedar Rapids – Chicago | 386 |
| DCA–RDU | Washington – Raleigh/Durham | 384 |
| PHX–TUS | Phoenix – Tucson | 382 |
| BHM–DFW | Birmingham – Dallas-Fort Worth | 368 |
| DAY–ORD | Dayton – Chicago | 366 |
| ATW–ORD | Appleton – Chicago | 364 |
| BOS–CMH | Boston – Columbus | 364 |
| JAX–ORD | Jacksonville – Chicago | 364 |
| DFW–MEM | Dallas-Fort Worth – Memphis | 363 |
| PHX–SMF | Phoenix – Sacramento | 363 |
| CAE–ORD | Columbia – Chicago | 361 |
| BNA–DFW | Nashville – Dallas-Fort Worth | 357 |
| DCA–IND | Washington – Indianapolis | 357 |
| CHA–ORD | Chattanooga – Chicago | 356 |
| ABE–ORD | Allentown/Bethlehem – Chicago | 353 |
| AMA–DFW | Amarillo – Dallas-Fort Worth | 351 |
| ALB–ORD | Albany – Chicago | 351 |
| MDT–ORD | Harrisburg – Chicago | 349 |
| DFW–LBB | Dallas-Fort Worth – Lubbock | 348 |
| CVG–MIA | Cincinnati / Covington – Miami | 345 |
| ORD–ORF | Chicago – Norfolk | 344 |
| ORD–ROC | Chicago – Rochester | 336 |
| DFW–OKC | Dallas-Fort Worth – Oklahoma City | 334 |
| HPN–ORD | White Plains – Chicago | 332 |
| DFW–HSV | Dallas-Fort Worth – Huntsville | 329 |
| CRP–DFW | Corpus Christi – Dallas-Fort Worth | 327 |
| CLT–SAV | Charlotte – Savannah | 325 |
| DFW–ICT | Dallas-Fort Worth – Wichita | 325 |
| BNA–CLT | Nashville – Charlotte | 321 |
| ORD–PVD | Chicago – Providence/Warwick | 316 |
| DFW–MTY | Dallas-Fort Worth – Monterrey | 316 |
| COU–ORD | Columbia – Chicago | 314 |
| IAH–PHX | Houston – Phoenix | 313 |
| AVL–ORD | Asheville – Chicago | 310 |
| BUR–PHX | Burbank – Phoenix | 310 |
| ORD–SYR | Chicago – Syracuse | 308 |
| BHM–CLT | Birmingham – Charlotte | 307 |
| DFW–STL | Dallas-Fort Worth – St Louis | 303 |
| BDL–ORD | Hartford – Chicago | 303 |
| BNA–TPA | Nashville – Tampa | 303 |
| DFW–HOU | Dallas-Fort Worth – Houston | 296 |
| DFW–MCI | Dallas-Fort Worth – Kansas City | 295 |
| ABQ–DFW | Albuquerque – Dallas-Fort Worth | 292 |
| BTR–DFW | Baton Rouge – Dallas-Fort Worth | 291 |
| BOI–PHX | Boise – Phoenix | 290 |
| DFW–MFE | Dallas-Fort Worth – McAllen | 288 |
| IAH–MIA | Houston – Miami | 283 |
| FWA–ORD | Fort Wayne – Chicago | 279 |
| DFW–ELP | Dallas-Fort Worth – El Paso | 274 |
| BWI–MIA | Baltimore – Miami | 273 |
| MLI–ORD | Moline – Chicago | 273 |
| BTV–ORD | Burlington – Chicago | 272 |
| CAE–CLT | Columbia – Charlotte | 269 |
| CLT–RIC | Charlotte – Richmond | 267 |
| DFW–MSY | Dallas-Fort Worth – New Orleans | 267 |
| DFW–JAN | Dallas-Fort Worth – Jackson | 266 |
| PHX–SJC | Phoenix – San Jose | 265 |
| CHS–ORD | Charleston – Chicago | 264 |
| CLT–GSO | Charlotte – Greensboro | 263 |
| ORD–ROA | Chicago – Roanoke | 263 |
| PHX–RNO | Phoenix – Reno | 263 |
| ELP–PHX | El Paso – Phoenix | 263 |
| DFW–SHV | Dallas-Fort Worth – Shreveport | 261 |
| CAK–ORD | Akron – Chicago | 260 |
| DCA–MCI | Washington – Kansas City | 260 |