High–speed tests of a North American P–51B aircraft were conducted in California in 1944 in order to study the correlation between wind tunnel and flight test drag data. At first, wind tunnel drag data was obtained using a highly accurate 1/3 scale model of the aircraft that was tested in the 16–foot wind tunnel of the Ames Aeronautical Laboratory. Then, flight test drag data was aquired by making a series of high–speed dives with a propellerless P–51B aircraft at Muroc Army Air Field in the Mojave Desert. During the flight tests the P–51B aircraft was towed to 28,000 ft by a Northrop P–61A airplane. Then, the pilot of the P–51B released the tow rope and the aircraft was dived to a high subsonic Mach number. Test data was recorded during the dive and, at the completion of the dive, the airplane was landed on the surface of Rogers Dry Lake. Three successful dives were performed that provided a limited amount of results for the data correlation. Unfortunately, the tow rope attachment on the P–61A aircraft broke during the fourth flight at an altitude of only 500 ft. The P–51B had to make an emergency landing in rough terrain. Miraculously, the pilot escaped the crash with only minor injuries. The aircraft, however, was damaged beyond repair and no further flights could be performed. Overall, the comparison of the wind tunnel and flight test drag data showed satisfactory agreement over the investigated Mach number range. This series of tests must be considered as one of the first successful attempts in the history of aircraft development to correlate wind tunnel and flight test data at transonic speeds.