My nephew, at around age three, used to say that airplanes trailing white exhaust were "airplanes on strings".
A childhood belief about aeroplanes

others believed things like this
- when i was little, i used to believe that airplanes goes out of space.Anon
- When I was little, I used to believe that airplanes took off like rockets.— Edene
- I used to believe airplanes were flying submarines.— Gullible isn't in the dictionary
- I used to believe that the roars from airplanes was the earth yawning.— Natasha
- I used to believe that airplanes would land in your yard and pick you up.— Rachel
- I used to believe airplanes were powered by magic carpets.— Anonymous