Flight 1420 was scheduled to depart DFW at 20:28 (8:28 PM) Central Daylight Time and arrive in Little Rock at 21:41 (9:41 PM). However, the flight crew was advised before boarding that the departure would be delayed, and that the National Weather Service had issued in-flight weather advisories indicating severe thunderstorms along the planned flight path. Adverse weather caused the plane that was intended for Flight 1420 to be delayed in arriving at DFW. Airline policy set a maximum pilot duty time of 14 hours, and Flight 1420 was the flight crew's last flight of the day. The first officer notified the airline's flight dispatcher that the flight crew would therefore be unable to depart after 23:16 (11:16 PM). The airline substituted another MD-80, tail number N215AA, which allowed Flight 1420 to depart DFW at 22:40 10:40 PM).