Dallas ? The first Southwest Airlines Co. flight from Dallas to Missouri left Love Field on Tuesday morning, opening a new front in the battle between the low-cost carrier and American Airlines.

The 8:10 a.m. flight to St. Louis was followed 40 minutes later by a flight to Kansas City, Mo., marking Southwest’s first new nonstop service from Love Field in more than 20 years.

A few hours later, American, the nation’s largest airline, announced that American and regional affiliate American Eagle would begin 16 daily flights from Love Field on March 2 to St. Louis, Kansas City, Austin and San Antonio.