On May 9, 2013, about 1446 central daylight time, Delta Air Lines flight 2071, an Airbus 320-200, registration N327NW, had a flight attendant who fell and suffered a serious injury. The flight was operating under the provisions of 14 CFR Part 121 as a scheduled domestic passenger flight from Detroit, Michigan, to Dallas, Texas.According to flight attendant (FA) statements, the 1L FA did not notice that the jumpseat had not stowed automatically and she tripped and fell when she reached over the seat to disarm the main door after arrival at the gate. A follow-on medical examination revealed that the FA had received serious injuries from the fall.