Southwest Airlines and Chili’s parent Brinker International have joined a group of retailers who are trying to create a mobile payment system to compete with Google Wallet, Dallas-based AT&T and credit card companies. The Dallas-based companies have become members of Irving-based Merchant Customer Exchange, a mobile payment system formed last year by some of the largest U.S. retailers. More than 30 companies are part of MCX including Wal-Mart, Target, Gap, 7-Eleven, Best Buy, Dillard’s, CVS, Lowe’s and QuikTrip. MCX is building a system that will work with bar code scanners already in stores and on the broadest array of smartphones. It says it wants to create “a widely accepted, customer-focused and secure mobile-commerce solution.” A timeline still hasn’t been disclosed, a spokesman said. Southwest is the first airline to join the group.