ORIGINAL: Fastsky
The planes engine is adjusted for high rpm and has no throttle. The pilot simply takes off and then flys the plane until the engine runs out of fuel.
This is not true in all cases. For instance, in C/L stunt, the engine is set for low RPM, 4 cycle. When the pilot pulls the model into a maneuver, it puts the engine under a load and causes it to revert to 2 cycle and increases RPM. In some forms of racing, the pilot has a control to shut off the fuel line and kill the engine.