August 10, 1920 – Chicago, Illinois
August 15, 1920 – Omaha, Nebraska
In September 1920, Amberg broke a speed record when he made the Maywood, Illinois – Omaha, Nebraska flight in 3 hours and 39 minute. He made the 440-mile flight in a de Havilland airmail airplane, stopping only once. He had to land at Iowa City, Iowa when his main gas tank sprung a leak and had to be disconnected. On his way to the field, he had flown the last fifteen miles pumping gas into the carburetor by hand.
Amberg left the airmail service a few days after breaking the speed record. He joined the army's air service and over the next year gave flying demonstrations around the country.