For its third flight, on 20 June 1959, the 01 was authorised to fly over the Paris Air Show at Le Bourget airport in front of France's President Charles de Gaulle. On 19 September 1960, René Bigand (replacing Glavany as test pilot) increased the world record for speed on a 1000-kilometre closed circuit to 1,822 km/h (1,132 mph) around Paris and the Melun base. Flight 138, on 23 September, corroborated the initial performance and pushed the record on a 500 km closed circuit to an average of 1,972 km/h (1,225 mph), flying between Mach 2.08 and Mach 2.14. The Mirage IV 01 prototype underwent minor modifications during testing in the autumn of 1959, most noticeably, the tail was enlarged (slight reduction in height, large increase in chord).