The Paper Airplane is a beta item in Animal Crossing. It cannot be obtained without the use of cheats.
The reasons for its removal are unknown, but the item still remains in a buggy state. When added to the inventory, it acts similar to a piece of paper, giving the player the option to "Read" or "Write a Letter". It is invisible when dropped, but running out of the acre it was dropped in and returning causes it to appear. It has the ability to spread and shut down acres. It may spread throughout the entire town, rendering the game unplayable. The areas it spreads to are altered by the Glowing Yellow Box.