The Flying Ionospheric Laboratory, a NKC-135 jet aircraft of the Air Force Cambridge Research Laboratories, made during the winter of 1969–1970 four flights which examined the continuity of the auroral oval. Two passed completely around the oval; two covered the afternoon-evening half of the oval. The all-sky camera photographs taken during, these flights strongly suggest that the auroral oval, defined as the band of visible auroral arcs, is under moderately disturbed magnetic conditions (ΣKp>10) a continuous band around the geomagnetic pole. Under quiet conditions (ΣKp<10) discontinuities in the occurrence of aurora in the oval were observed in the morning, noon, and evening sector. Discontinuities in the morning sector were of temporal nature, the discontinuities in the noon and evening sector could be either temporal or spatial.