Utilize the input text as a context reference, choose the right relationship between Southwest Airlines and Dallas from the options. Options: product/material produced, manufacturer, distributed by, industry, position held, original broadcaster, owned by, founded by, distribution format, headquarters location, stock exchange, currency, parent organization, chief executive officer, director/manager, owner of, operator, member of, employer, chairperson, platform, subsidiary, legal form, publisher, developer, brand, business division, location of formation, creator.

"We have not grown Southwest Airlines in three or four years," but now "we have opportunities to grow like we haven't had in years," CEO Gary Kelly said, citing Dallas and Houston.

Answer: location_of_formation