The Lockheed F-117 Nighthawk first flew in 1981 and was operational from 1983, but the US Air Force did not acknowledge its existence until 1988. It was the first aircraft designed from the outset to defeat radar, and it looks like nothing before or since.
The Soviet paper
The theoretical basis came from an unexpected source. In 1962 the Soviet physicist Pyotr Ufimtsev published a paper on the mathematics of electromagnetic wave diffraction from geometric shapes.
The work was considered of purely academic interest in the Soviet Union and was not classified. It was translated and published in the West, where a Lockheed engineer named Denys Overholser found it in the mid-1970s.
Ufimtsev's equations allowed the radar reflection of a flat surface to be predicted precisely. That made it possible, with the computing power of the era, to design an aircraft from flat panels arranged so that incoming radar energy is reflected away from the transmitter rather than back to it.
Why it is faceted
The F-117's angular appearance is a direct consequence of 1970s computing limits. The mathematics could handle flat plates; it could not handle curved surfaces at that scale.
So the aircraft was built from flat facets — hundreds of them — each angled to scatter radar energy in a controlled direction. The result was aerodynamically poor and needed a computerised flight control system to remain stable at all, which is why the aircraft was nicknamed the Hopeless Diamond during development.
By the time the B-2 was designed a decade later, computing had advanced enough to model curved surfaces, which is why the B-2 is smooth and the F-117 is not.
Operations
The F-117 flew at night, without radar of its own — using a radar emits a signal, which defeats the purpose — navigating by inertial systems and attacking with laser-guided bombs through infrared targeting.
It saw action in Panama in 1989 and prominently in the 1991 Gulf War, where F-117s struck heavily defended targets in Baghdad on the first night. Their apparent invulnerability shaped public perception of the war.
The one that was shot down
On 27 March 1999, a Serbian anti-aircraft unit shot down an F-117 over Yugoslavia using a modified S-125 system. The pilot ejected and was rescued.
The Serbian battery commander had adapted his tactics: using long radar wavelengths, keeping emissions brief, and relying on visual observers along known flight routes. The F-117 had flown similar routings repeatedly, which made prediction possible.
Wreckage was recovered and is widely reported to have been examined by Russian and other intelligence services.
What it established
Stealth as a design discipline. Everything that followed — the B-2, the F-22, the F-35, and the equivalent programmes in other countries — descends from the F-117's demonstration that radar cross-section can be engineered.
The F-117 was retired in 2008, though aircraft have been observed flying since, apparently in test and adversary training roles. It is one of the few aircraft whose entire operational concept came from a Soviet academic paper nobody thought was important.