All-sky camera photographs from flights of the Air Force Geophysics Laboratory (AFGL) airborne ionospheric observatory have been used to investigate discrete auroras in the midnight sector of the auroral oval. The photographs were taken at intervals of 1 min throughout flight durations of 5--10 hours near 69 ¿ (¿4 ¿) corrected geomagnetic latitude; the 12 flights totaling 93 hours provide ~5600 frames. For each flight the photographs have been assembled into a montage format which permits perception of individual frames and also, in the aggregate, reveals individual events of auroral activation with measurable lifetimes. The discrete auroras observed in this way, when classified into four categories of activity, active (A), moderate (M), quiet (Q), and no discrete aurora visible (N), exhibit frequencies of occurrence of 22, 37, 24, and 17%, respectively. The lifetimes of auroras in categories A, M, and Q occur predominantly in a group which maximizes between 10 and 20 min with another lesser group which maximizes near 2 hours. Ten to 20 min is also characteristic of the duration of plasma flows observed in the plasma sheet, and thus it is suggested that discrete auroras may be associated with these flows.