movies of the tests, it was decided that the bouncing was probably caused by unwanted rudder movements. The control system was modified so that the joystick controlled the elevons rather than the rudder, which solved the problem. It was found that the car used to tow the aircraft was not powerful enough to lift the M2-F1 entirely off the ground, so the FRC arranged to have the tow car hot-rodded by Bill Straub: the modifications tuned the engine for increased power, added a rollbar, and turned the front passenger seat to face aft so the passenger could observe the aircraft. This proved successful, and tow tests continued. Speeds on tow inched up to , which allowed Thompson to climb to about , then glide for about 20 seconds after releasing the line. That was the most that could be expected during an auto tow. These initial tests produced enough flight data about the M2-F1 to proceed with flights behind a U.S. Navy C-47 tow plane at greater altitudes. Flight testing A NASA C-47 was used for all of the air tows. The first was on August 16, 1963. The M2-F1 had recently been equipped with an ejection seat and small rockets – referred to by the test team as "instant L/D" – in the tail to extend the landing flare for about 5 seconds if needed, and Thompson prepared for the flight with a few more tows behind the Pontiac. Forward visibility in the M2-F1 was very limited on tow, requiring Thompson to fly about higher than the C-47, so he could see the plane through the nose window. Towing speed was about . The C-47 took the craft to an altitude of , where free flights back to Rogers Dry Lake began. Pilot for the first series of flights of the M2-F1 was NASA research pilot Milt Thompson. Typical glide flights with the M2-F1 lasted about two minutes and reached speeds of . Tow release was at . The lifting body descended at an average rate of about 3,600 feet per minute (1,100 m/min). At above the ground, the nose was lowered to increase speed to about , flare was at from a 20° dive. The landing was smooth, and the lifting-body program was on its way. The M2-F1 was flown until August 16, 1966. It proved the lifting-body concept and led the way for subsequent metal "heavyweight" designs.