Shares of Delta Air Lines, Inc. (NYSE: DAL) inches up in pre trading session on Tuesday as during the epidemic, U.S. airlines depended on loyalty programs for revenue, and industry officials and analysts said the programs' revenues should stay up even if the economy enters a recession. The programs, which were introduced more than 40 years ago to foster airline brand loyalty, are now a source of income for the airlines through the selling of miles to third-party partners, mostly banks that issue credit cards and award the miles to...