Taking an off the shelf free flight glider and turning it into an RC motorized airplane, using micro brushed motors to power its flight, a very fun and simple project to make.
This is an airplane you can buy for about $10 on ebay, you can find even bigger models, and then buy the electronics to make your first RC airplane yourself.
Gotta Know Joe Hobbies in Spring Tx Proving that R/C airplanes do not need to be expensive This plane was found and rescued from a hot damp old Conex storage container