Donald A. Hall  Donald Albert Hall (December 7, 1898 – May 2, 1968) was an American pioneering aeronautical engineer and aircraft designer who is most famous for having designed the "Spirit of St. Louis". Hall was also part of the three-person team that discovered that the crack of a bullwhip is a sonic boom. Hall was born in Brooklyn, New York on December 7, 1898. He attended the Manual Training High School in Brooklyn, and graduated from the Pratt Institute with a certificate in Industrial Mechanical Engineering in 1917. From 1919 to 1921, Donald Hall worked for the Curtiss Aeroplane and Motor Company as a junior draftsman, checker, and then designer. From 1921 to 1922, he was the aerodynamic design and acting chief engineer at Elias & Brothers. He moved to Santa Monica, California in 1924 to work for Douglas Aircraft. He left Douglas Aircraft in 1926, briefly worked for the airplane division of Ford Motor Company, and then became an aviation cadet in the U.S. Army Air Corps, but did not become a military pilot. He returned to Douglas Aircraft, and joined Ryan Airlines in San Diego on 31 January 1927 as a full-time chief engineer and parts inspector, three weeks before Charles Lindbergh visited the company to design the "Spirit of St. Louis"  Only days later, Ryan Airlines received an inquiry from Robertson Aircraft Corp. of St. Louis asking if they could design and build an aircraft capable of flying nonstop from New York to Paris. Ryan Airlines responded in the affirmative and after all the other potential manufacturers had said no, Charles A. Lindbergh finally traveled to San Diego on 21 February 1927 to inspect the Ryan Airlines facility. There he met Donald Hall for the first time. After touring the facility with the new owner Benjamin Franklin Mahoney, Lindbergh met and discussed the project with Donald A. Hall in his second story office. Lindbergh wanted to decide if the company could really deliver on the proposed aircraft. Lindbergh later stated in his Pulitzer Prize winning 1953 book, "The Spirit of St. Louis", that he chose Ryan Airlines in part because he believed in Hall's ability. The two men began working closely to design and construct the aircraft in only sixty days, from 28 February 1927 to 28 April 1927 when the first flight tests started. Upon the request of Charles Lindbergh, Donald Hall intentionally left the wings small to keep the aircraft slightly unstable and keep its aviator awake. The final aircraft was known as the Ryan NYP (registration number N-X-211) which captured popular imagination as the "Spirit of St. Louis" in May 1927 by flying nonstop from New York to Paris.