Dallas Love Field was the original airport, and when the new International Airport opened in 1974, the cities of Dallas and Fort Worth, presumably in an attempt to see it succeed, tried to stop interstate flights (i.e. flights from Texas to some other state) from flying out of Love Field.
In 1979, however, the U.S. Congress passed the Wright Amendment. This allowed large aircraft to fly from Love Field to to locations in Arkansas, Louisiana, Oklahoma and New Mexico. This was expanded by the passage of the Shelby Amendment in 1997 which allowed flights to Alabama, Kansas and Mississippi as well.
This is relevant (and I use that word in its most limited sense) primarily because of how it affects Southwest Airlines, a major U.S. discount carrier. Southwest uses Love Field as their airport in Dallas and, as such, cannot fly from Dallas to anywhere outside of Texas, Louisiana, Arkansas, Oklahoma, New Mexico, Mississippi, and Alabama.
If you look at Southwest’s route map you can see that Dallas, a large
metropolis, is smack dab in the middle of a lot of the U.S. (see the photo of the U.S. from space on this page to see this very clearly). And thus not being able to use Dallas as a jumping off point to the rest of the U.S. is a logistical problem for the airline; it even warrants its own page on their website.
I experienced this restriction personally back in the early 1990s when I wanted to fly from El Paso to Detroit on Southwest. I was routed El Paso, Austin, Houston, St. Louis, Chicago, Detroit. If you look at the map, El Paso to Dallas would have been the logical first step, the law notwithstanding.