Let's Fly Mechanical Airplane Toys
Toys that fly? The RC airplane industry is huge. But we don't talk RC here. We love the good old mechanical stuff. Can airplanes be mechanical? Sure. Some of them even fly. Let's see:
Free flight airplanes
Free flight airplanes don't have that much (or any) mechanics in them. They are just light static aircraft models that are thrown by hand or kind-of trebuchet and let the wind bring them away. The most important thing about them is to be light, robust and aerodynamical. There are often no moving parts in them. Some have rotating propeller like the one on the picture below:
Rubber band airplanes
Picture courtesy of modelairplanes.com
But wait! Some mechanical model airplanes actually have mechanics! And they allow them to fly, usually longer and better than the planes thrown by hand. These airplanes use a simple rubber band mechanism that winds up and unwinds the propeller during the flight. Don't expect wonders from this "engine" - usually such mechanism can't raise the airplane from the ground and it still should be "powered" by hand. But the rotating propeller certainly makes the flight more stable and longer.
This article here explains the rubber band airplane mechanics in great details. It's not a hard task to make one of these yourself even with basic skills. If you prefer to buy a ready one, you can find many on Amazon and they are not expensive.
Non-flying models
Not every airplane has to fly. Unless it's not a toy :D In fact some of the most fascinating mechanical airplane toys are non-flying. They can be wooden models of real airplanes - with ot without gears that demonstrate some movement. They can be also entirely static plastic scale models. Some have simple mechanisms that allow them be driven on the ground but not to fly. These can all be excellent and educational toys so don't underestimate them.
Pedal and ride-on airplanes
Having little kids? Here's another toy idea: a big ride-on airplane where the kid can sit in and pretend to be a pilot. This can be a classical spring ride-on toy in the background or a pedal-powered airplane that can be used even indoors. Such a toy can be quite a lot of fun.