Douglas X - 3 Stiletto The Douglas X - 3 Stiletto was a 1950s United States experimental jet aircraft with a slender fuselage and a long tapered nose , manufactured by the Douglas Aircraft Company . Its primary mission was to investigate the design features of an aircraft suitable for sustained supersonic speeds , which included the first use of titanium in major airframe components . Douglas designed the X - 3 with the goal of a maximum speed of approximately 2 , 000 m . p . h , but it was , however , seriously underpowered for this purpose and could not even exceed Mach 1 in level flight . Although the research aircraft was a disappointment , Lockheed designers used data from the X - 3 tests for the Lockheed F - 104 Starfighter which used a similar wing design in a successful Mach 2 fighter . Design and development . The Douglas X - 3 Stiletto was the sleekest of the early experimental aircraft , but its research accomplishments were not those originally planned . It was originally intended for advanced Mach 2 turbojet propulsion testing , but it fell largely into the category of configuration explorers , as its performance ( due to inadequate engines ) never met its original performance goals . The goal of the aircraft was ambitious — it was to take off from the ground under its own power , climb to high altitude , maintain a sustained cruise speed of Mach 2 , then land under its own power . The aircraft was also to test the feasibility of low - aspect - ratio wings , and the large - scale use of titanium in aircraft structures . The design of the Douglas X - 3 Stiletto is the subject of U . S . Design Patent # 172 , 588 granted on July 13 , 1954 to Frank N . Fleming and Harold T . Luskin and assigned to the Douglas Aircraft Company , Inc . Construction of a pair of X - 3s was approved on 30 June 1949 . During development , the X - 3 ' s planned Westinghouse J46 engines were unable to meet the thrust , size and weight requirements , so lower - thrust Westinghouse J34 turbojets were substituted , producing only 4 , 900 lbf ( 21 . 8 kN ) of thrust with afterburner rather than the planned 7 , 000 lbf ( 31 . 3 kN ) . The first aircraft was completed and delivered to Edwards Air Force Base , California , on 11 September 1952 . The X - 3 featured an unusual , rakish shape of a long cylindrical fuselage with tiny trapezoidal wing s . One of the design considerations was to create the smallest and " thinnest " shape possible in order to achieve a streamlined planform . The extended nose was to allow for the provision of test equipment while the semi - buried cockpit and windscreen was designed to alleviate the effects of " thermal thicket " conditions . The low aspect ratio , unswept wings were designed for high speed and later the Lockheed design team used data from the X - 3 tests for the similar F - 104 Starfighter wing design . Due to both engine and airframe problems , the partially completed second aircraft was cancelled , and its components were used for spare parts . Operational history . The first X - 3 " hop " was made on 15 October 1952 , by Douglas test pilot William Bridgeman . During a high - speed taxi test , Bridgeman lifted the X - 3 off the ground and flew it about 1 mi ( 1 . 6 km ) before settling back onto the lakebed . The official first flight was made by Bridgeman on 20 October , and lasted about 20 minutes . He made a total of 26 flights ( counting the hop ) by the end of the Douglas tests in December 1953 . These showed that the X - 3 was severely underpowered and difficult to control . Its takeoff speed was an unusually high 260 kts ( 482 km / h ) . More seriously , the X - 3 did not approach its planned top speed . Its first supersonic flight required that the airplane make a 15° dive to reach Mach 1 . 1 . The X - 3 ' s fastest flight , made on 28 July 1953 , reached Mach 1 . 208 in a 30° dive . A plan to re - engine the X - 3 with rocket motors was considered but eventually dropped . With the completion of the contractor test program in December 1953 , the X - 3 was delivered to the United States Air Force . The poor performance of the X - 3 meant only an abbreviated program would be made , to gain experience with low - aspect ratio wings . Lieutenant Colonel Frank Everest and Major Chuck Yeager each made three flights . Although flown by Air Force pilots , these were counted as NACA flights . With the last flight by Yeager in July 1954 , NACA made plans for a limited series of research flights with the X - 3 . The initial flights looked at longitudinal stability and control , wing and tail loads , and pressure distribution . NACA pilot Joseph A . Walker made his pilot checkout flight in the X - 3 on 23 August 1954 , then conducted eight research flights in September and October . By late October , the research program was expanded to include lateral and directional stability tests . In these tests , the X - 3 was abruptly rolled at transonic and supersonic speeds , with the rudder kept centered . Despite its shortcomings , the X - 3 was ideal for these tests . The mass of its engines , fuel and structure was concentrated in its long , narrow fuselage , while its wings were short and stubby . As a result , the X - 3 was " loaded " along its fuselage , rather than its wings . This was typical of the fighter aircraft then in development or testing . These tests would lead to the X - 3 ' s most significant flight , and the near - loss of the aircraft . On 27 October 1954 , Walker made an abrupt left roll at Mach 0 . 92 and an altitude of 30 , 000 ft ( 9 , 144 m ) . The X - 3 rolled as expected , but also pitched up 20° and yawed 16° . The aircraft gyrated for five seconds before Walker was able to get it back under control . He then set up for the next test point . Walker put the X - 3 into a dive , accelerating to Mach 1 . 154 at 32 , 356 ft ( 9 , 862 m ) , where he made an abrupt left roll . The aircraft pitched down and recorded an acceleration of - 6 . 7 " g " ( - 66 m / s² ) , then pitched upward to + 7 " g " ( 69 m / s² ) . At the same time , the X - 3 side - slipped , resulting in a loading of 2 " g " ( 20 m / s² ) . Walker managed to bring the X - 3 under control and successfully landed . The post - flight examination showed the fuselage had been subjected to its maximum load limit . Had the acceleration been higher , the aircraft could have broken up . Walker and the X - 3 had experienced " roll inertia coupling , " in which a maneuver in one axis will cause an uncommanded maneuver in one or two others . At the same time , several North American F - 100 Super Sabre s were involved in similar incidents . A research program was started by NACA to understand the problem and find solutions . For the X - 3 , the roll coupling flight was the high point of its history . The aircraft was grounded for nearly a year after the flight , and never again explored its roll stability and control boundaries . Walker made another 10 flights between 20 September 1955 and the last on 23 May 1956 . The aircraft was subsequently retired to the U . S . Air Force Museum . Although the X - 3 never met its intention of providing aerodynamic data in Mach 2 cruise , its short service was of value . It showed the dangers of roll inertia coupling , and provided early flight test data on the phenomenon . Its wing planform was used in the Lockheed F - 104 Starfighter , and it was one of the first aircraft to use titanium . Finally , the X - 3 ' s very high takeoff and landing speeds required improvements in tire technology . Production . Two aircraft were ordered , but only one was built . It made 51 flights .