Followed by a Lockheed F-104A Starfighter chase plane, the North American X-15 ship #3 (56-6672) sinks toward touchdown on Rogers Dry Lake following a research flight. In the foreground is green smoke, used to indicate wind direction. The F-104 chase pilot joined up with the X-15 as it glided to the landing. The chase pilot was there to warn the X-15 pilot of any problems and to call out the altitude above the lakebed. F-104 aircraft were also used for X-15 pilot training to simulate the landing characteristics of the rocket-powered airplane, which landed without engine power since the rocket engine had already burned all of its propellant before the landing. The F-104s could simulate the steep descent of the X-15 as it glided to a landing. They did this by extending the landing gear and speed brakes while setting the throttle to idle.