ATLANTA, Jan 24 (Reuters) - Delta Air Lines Inc. (DAL), the No. 3 U.S. carrier, on Thursday said it will replace 50-seat regional jets on Delta Connection flights with new 70-seat Bombardier (BBDb) CRJ-700 planes in nine cities starting April 7 and May 1. The expanded flights beginning in April are between Atlanta and six markets: Augusta, Georgia; Huntsville, Alabama; Fort Wayne, Indiana; Toledo, Ohio; and Sarasota and Tallahassee, Florida. In May, 70-seat regional jet service will be added between Atlanta and Daytona Beach, Florida; Long Island/Islip, N.Y.; and Mobile, Alabama. Delta connection will o¾úú¢Ý½` ¥±åoundtrip flights at Toledo and all of the other markets will be once daily. All of the flights replace existing ones currently operated with the 50-seat CRJ-200 series of planes.