The story of YF-23 began in the early 1980s, during the peak of Cold War delusions. In Europe, the number of NATO troops is only one fourth of that of the Warsaw Pact. Faced with the fear that the MiG-29 and Su-27 may surpass the F-15 Eagle fighter jet, the Pentagon has begun to seek solutions.

The US Air Force has begun collecting information and data on Soviet made fighter jets in order to manufacture new fighters that can overcome this threat. Despite initial concerns about "pivot" and "sideguard" fighter jets, research shows that the real challenge comes from long-range air defense radar and surface to air missiles. Subsequently, the Pentagon formulated the basic characteristics that the next generation of fighter jets must possess: they must be more maneuverable than Soviet fighter jets, capable of cruising at supersonic speeds without the need for afterburning (while still retaining afterburning capabilities), combined with low observability (LO) technology to enable them to fly without surveillance (now known as stealth), the aircraft must be reliable and maintainable under adverse conditions, and it must have sufficient survivability to protect pilots and boost their confidence. In short, this will be a fighter jet far beyond any previous design. The project cost once reached over one million US dollars per day, jointly borne by the US government and the aviation industry.

In 1983, seven companies responded to the request for proposals and submitted their own design proposals, but the Pentagon ultimately chose only two. In 1986, Lockheed and Northrop were awarded contracts to manufacture two prototype aircraft each, which would compete with each other for a massive $2 billion defense contract. The fierce competition for the Advanced Tactical Fighter (ATF) project officially began.

Due to the large scale of the project, neither company was able to complete the task alone, so Lockheed teamed up with Boeing and General Dynamics, while Northrop gathered old friend McDonnell Douglas. The two companies had previously collaborated on the F/A-18 Hornet carrier based fighter jet project.

When the Northrop ATF R&D team was first formed, CEO Thomas Jones gave these engineers and scientists a simple instruction: "Guys, innovate boldly

The Pentagon has classified ATF as top secret, with the code name "Senior Sky" for this black program.

Del Jacobs was appointed as the Design Phase Manager for the Northrop ATF project, and his team initially consisted of only four people, but quickly grew.

They began a four-year exploration, during which the team lived and breathed in with the YF-23 project. They typically worked 7 days a week, 14 hours a day, and they referred to it as the battle between Northrop's David and Lockheed's Goliath.

The expanding team is isolated in a large secretive building of Northrop Corporation, which has no signage or windows. The staff of the ATF project must park their vehicles away from the building to avoid a sudden increase in parking numbers that could alert Soviet spy satellites.