(in cooperation with AstroPilot.info)
Photograph Explanation:

Noctilucent Clouds. This image was taken 15 June 2004 while airborne at 37,000 feet. From this position over the mid-North Atlantic Ocean (near 56N, 030W) it would have been perpetual Arctic twilight and on this occasion the Noctilucent Clouds were straight overhead. A routine passing of another jet aircraft gave perspective as to how much higher and farther away the NLC were, a factor of 10x. An incredible sight! Photo: BrianWhittaker (.com) as seen on www.SpaceClouds.info.