Northop's Stealth Aircraft: Prototypes and Projects 1940-1950. War Secrets

On September 18, 1948, the YB-49 (42-102367) piloted by Northrop´s chief test pilot Max Stanley, flew over the Air Defense Station at Half Moon Bay, to the south of San Francisco, undetected by the powerful radar TPS-10, that had a range coverage of 120 nautical miles and a height-finding of 60,000 feet. When the technicians of the 636th Squadron, Detachment G, visually located the strange plane flying over the Air Defense Direction Centre informed the 636th staff in Kirkland AFB.
The incident caused great concern among the US political and military leadership as huge sums had already invested in the creation of the LASHUP system, a chain of radar stations for the air defense of USA that they had already started to install.
Northrop engineers were incredulous and decided to carry out detailed tests on the stealth features of the YB-49. To that purpose they performed a series of flights during which a P-61C night fighter used its APS-720 AI radar to scan the bomber from different angles with conclusive results.
The bomber repeatedly made invisible passes over civil and military radar stations that picked up other aircraft.
It was known that the Soviets had captured the scientist Dr. Günther Bock in Eilenburg on April 29, 1945, together with two Horten prototypes, all the drawings of the Ho VIII buried by Horten employees of the Sonderkommado 9 near Kilenburg, a complete set of plans of the Ho IX and several engineers of the Gothaer Waggonfabrik Flugzeugbau firm, with extensive knowledge on RAM techniques.
In the ‘June 9, 1947 intelligence report’, the U.S. attaché in Moscow Major Edison K. Walters informed the War Department that the Soviets had started the production of a jet powered version of the Horten Ho VIII, with 131 feet wingspan and thirty-three thousand pounds max weight. The information was false, but the fear of losing technological superiority to the Soviets in the field of radar, and the possibility of Soviet-built stealth bombers, generated significant disagreements regarding defense strategy between the Department of Defense and the Northrop firm.