What's this tiny airplane?
I would make this a comment since I can't be certain, but I wanted to put some photos in. I concur with Ron that it's a target drone. But what target drone?

The one next to it appears to be a Ryan BQM-34 Firebee. 

The most likely possibility is the Beachcraft MQM-107 Streaker. 

Here is a chart of US target drones.


source