The last time my family went to see the air show in Anchorage, I think I was 12 or so. Maybe younger. Thunderbirds at the Alaska Air Show in Anchorage, Alaska. They have been to Anchorage many times in the summer!
Humans sometimes make cloud formations without realizing it. High-flying military planes and low-flying commercial planes cause disturbances in clouds. By doing so, they create their own formations. These aren't "real" cloud formations, of course,