When starting across country, particularly in the early days, a pilot had to consider very seriously the question of the failing of his motor. So long as he had an aerodrome below him, its smooth surface providing an alighting spot, he felt no great concern. But in flying across country, should his motor stop, he might find himself above a forest, or a sheet of water, or such rough and broken land that his machine would be damaged were he to alight upon it. But here again, as in the case of side-slip, altitude would tend to safety. In the stoppage of its motor, when a craft is in flight, several factors need consideration; but one should clearly be understood: even if his engine does fail while he is passing through the air, a pilot is not helpless, nor does his machine fall to the ground. As he flies, of course, it is the thrust of his motor, acting through the medium of the propeller, that keeps his craft moving forward; and so long as this thrust is there, forcing his planes against the air and causing them to lift their load, the machine will fly ahead. But what happens should the engine fail, and the machine cease to be propelled? The first effect is that the craft begins to lose its speed, and as it does this its planes are less operative. Unless he can restore his forward speed, therefore, and so maintain the lift of his planes, the pilot is in peril. Were he merely to sit still after his engine failed, and do nothing to save himself, he would be in a position of the greatest risk. What would happen would be that his craft, having no power thrusting it against the air, would come gradually to a standstill; then, its planes exercising no further lift, it would lose equilibrium and fall.