[rockinghigh]

> There are very few airlines that offer more legroom

United Premium, United Premium Plus, Delta Premium Select, American Airlines Premium Economy, Lufthansa Premium Economy, Alaska Airlines Premium Class, Air France Premium Economy, Air China Premium Economy...

[chipotle_coyote]

AFAIK, most of those aren't available on domestic US flights. If you're flying internationally, it's almost always been possible to spend more to get more space and service, sometimes up to rather eye-watering levels, but flights within the US tend to be limited to economy and first class. (Some economy seats do have more leg room than others and carry a premium charge, but the OP may still be technically correct based on the "very few" condition.)