Packard, known as the Master Motor Builders, made some of the world's best engines for both automobiles and aircraft. It first manufactured aircraft engines during World War I and continued after that war. Packard used the nearly mile-long infield of the Proving Grounds automotive test track as a landing strip. Engineers refined the world's first Diesel radial aircraft engine, the DR-980, in the aircraft hangar at the test track, and Packard test pilots proved the engine's superior range and safety. On August 15, 1929, aviator Charles Lindbergh visited the Proving Grounds for a test flight of the DR-980 in a Stinson airplane. The first flight of a fixed-wing aircraft with a diesel radial engine occurred at the Packard Proving Grounds on September 18, 1928.