Two sets of observations from a NASA U-2 airplane looking down on the tops of nocturnal thunderstorms are reported. Photographs show both diffuse illumination in the cloud and unobscured segments of lightning channels a kilometer or longer in clear air around and above the cloud. Multiple images of lightning channels indicate multiple discharges in the same channel. Lightning spectra were obtained similar to those observed beneath cloud base. Field changes correlate with pulses measured with a photocell optical system. Optical signals corresponding to dart leader, return stroke, and continuing current events are readily distinguished in the scattered light emerging from the cloud surface. The variation of light intensity with time in lightning events such as dart leaders, which radiate light first from a location within the cloud and later from outside (beneath) the cloud, are consistent with the predicted modification of optical lightning signals by clouds as given by Thomason and Krider (1982). As a result it appears that satellite based optical sensor measurements cannot provide reliable information on current rise times in return strokes. On the other hand, discrimination between cloud-to-ground and intracloud flashes and the counting of ground strokes is possible, using the optical pulse pairs identified with leader, return stroke events in the cloud-to-ground flashes studied. If confirmed by further studies as a regularly identifiable occurence, the pulse pairs, together with other criteria, could form the basis for the reliable identification of ground strokes from a satellite. A multitude of weak lightning channels commonly exists in the clear air above or around cloud tops, indicating that lightning is capable of introducing chemical species, ions, and space charge directly into the upper troposphere and lower stratosphere.