Take a look at the photos of my model. The close-up with me standing against the airplane. Look to the right and you'll see a small box sticking up in front of the windshield. That is the timer for the electric motor. It is available from Hi-Line in North Carolina a company owned by Dave Rees who is a well known scale free flight modeler. Anyway, this timer is adjustable and is energized by the touch of a 9V battery across two wire contacts that serve as an instant on switch. They are relatively cheap and work every time. The only disadvantage is that once it's on you can't shut it off unless you wire in a separate kill switch.