DALLAS, Texas - Southwest Airlines has moved up its timetable to begin direct flights between Tulsa and Chicago's Midway Airport.

The airline announced last year that the start date would be June 2, 2013. But it now says the flights will begin on April 15th.

Southwest says the reason for the change was the availability of new aircraft in its fleet, due in part to the integration of AirTran by Southwest.

Southwest already has flights between the two cities, but passengers must stop at another designation before going on to either Tulsa International or Chicago's Midway.