advanced form, sweep theory led to the experimental oblique wing concept. Adolf Busemann introduced the concept of the swept wing and presented this in 1935 at the 5. Volta-Congress in Rome. Sweep theory in general was a subject of development and investigation throughout the 1930s and 1940s, but the breakthrough mathematical definition of sweep theory is generally credited to NACA's Robert T. Jones in 1945. Sweep theory builds on other wing lift theories. Lifting line theory describes lift generated by a straight wing (a wing in which the leading edge is perpendicular to the airflow). Weissinger theory describes the distribution of lift for a swept wing, but does not have the capability to include chordwise pressure distribution. There are other methods that do describe chordwise distributions, but they have other limitations. Jones' sweep theory provides a simple, comprehensive analysis of swept wing performance. An explanation of how the swept wing works was offered by Robert T. Jones: "Assume a wing is a cylinder of uniform airfoil cross-section, chord and thickness and is placed in an airstream at an angle of yaw – i.e., it is swept back. Now, even if the local speed of the air on the upper surface of the wing becomes supersonic, a shock wave cannot form there because it would have to be a sweptback shock – swept at the same angle as the wing – i.e., it would be an oblique shock. Such an oblique shock cannot form until the velocity component normal to it becomes supersonic." To visualize the basic concept of simple sweep theory, consider a straight, non-swept wing of infinite length, which meets the airflow at a perpendicular angle. The resulting air pressure distribution is equivalent to the length of the wing's chord (the distance from the leading edge to the trailing edge). If we were to begin to slide the wing sideways (spanwise), the sideways motion of the wing relative to the air would be added to the previously perpendicular airflow, resulting in an airflow over the wing at an angle to the leading edge. This angle results in airflow traveling a greater distance from leading edge to trailing edge, and thus the air pressure is distributed over a greater distance (and consequently lessened at any particular point on the surface). This scenario is identical to the airflow experienced by a swept wing as it travels through the air. The airflow