On May 21, Paul Tengesdal boarded a plane at the Gardermoen Airport in Oslo, Norway. A few minutes later he saw something unusual in the window. As he said, a bright glowing letter “X” hovered among the clouds, which he took on the camera of his iPhone 7. According to him, it could be watched less than two minutes, and as soon as the plane left the cloud zone, it disappeared.
Tengesdal witnessed a rare type of halo – arc around the antisolar point. To observe the phenomenon, one must look directly from the sun, looking down at the icy clouds, where subhorizontal reflections from the faces of the ice crystals create these strange arcs.
The place of Tengesdal on the plane was ideal for such observation for two short minutes. He was just sitting on the side, diametrically opposite to the Sun. The plane’s shadow appeared in the diamond-shaped center “X” (at the antisolar point-the point directly opposite to the Sun), and the clouds were hovered by a thin layer under the airplane.
Antisolar arcs are bright, but elusive – their observation requires that the passenger is sitting in the right place, looking in the right direction at the very moment when the plane rises above the icy clouds. All this makes the observation of such a phenomenon a rarity.