Delta Air Lines System Timetable May 1, 1991
MLA
Delta Air Lines, Inc.. "Delta Air Lines System Timetable May 1, 1991." Delta Flight Museum. 1991-05-01, https://dlg.galileo.usg.edu/do:delta_dal-tt_dal-tt-19910501.
APA
Delta Air Lines, Inc. (1991-05-01). Delta Air Lines System Timetable May 1, 1991. Retrieved from https://dlg.galileo.usg.edu/do:delta_dal-tt_dal-tt-19910501
Chicago
Delta Air Lines, Inc.. "Delta Air Lines System Timetable May 1, 1991." 1991-05-01. February 22, 2026. https://dlg.galileo.usg.edu/do:delta_dal-tt_dal-tt-19910501.
