I saw this story, and I was instantly transported to my childhood.
National Geographic News - Planes Change Weather
I thought that the planes in the sky made clouds, and thus made the rain. What was I supposed to think? With the vaporous jet stream pouring out of the back... it would stay long after the plane was out of sight. In my immature mind I explained that the thin stream was like a seeding. They grew into storms over time.
I may have been on to something... I must've been some kind of untapped child prodigy. hmph.