This is the story of two brothers, who happen to be airplanes. The older brother, the F-15 Eagle, entered the world fully formed, and his doting parents—the U.S. Air Force—nurtured him and quickly forgave minor transgressions. The younger brother, the F-16, was born prematurely, with no name, and scrambled to catch up. At a rollout ceremony on December 13, 1973, in Fort Worth, Texas, the YF-16 faced its skeptics and a few champions with a gaudy red, white, and blue paint job. After the ceremony, the airplane was flown on a C-5 to Edwards Air Force Base in California to prepare for its first flight.

On January 20, 1974, during a high-speed taxi test, General Dynamics test pilot Phil Oestricher applied what he thought were small control-stick inputs in the standard method used to check the airplane’s roll response. However, in response to the pilot’s input, the control stick in the YF-16, mounted on the right instead of the customary center, didn’t actually move. Instead, it measured the pressures exerted by the pilot’s hand and relayed that data, via electronic sensors, to hydraulic actuators in a newfangled fly-by-wire control system. The simulator Oestricher had flown didn’t adequately portray the stick forces, so he hadn’t learned to judge how much aileron he was commanding.

Too much, apparently. The YF-16 oscillated wildly, banging the right elevator on the runway. After struggling with the aircraft, Oestricher decided it would be safer to take off. The test director, retired Colonel Jim Rider, remembers being “up in the control tower, watching my career go down the tubes.”

The short flight and landing were uneventful, no one got fired, and General Dynamics scheduled the first official flight for February 2. Retired Colonel Bob Ettinger, a YF-16 test pilot, was assigned to investigate the cause of the incident. He concluded that it “resulted from flying an antiquated flight test technique that didn’t work for a fly-by-wire system.” It would be one of many lessons taught by the new arrival.

One of two entries in the Air Force’s Lightweight Fighter (LWF) technology demonstration program (the other was the Northrop YF-17), the YF-16 used Pratt & Whitney F100 engines from the McDonnell Douglas F-15. It picked up existing components from other aircraft, including landing gear tires from a Convair B-58 bomber. What the YF-16 had that was all its own was an unstable, and therefore highly maneuverable, airframe that could withstand 9 Gs and, to manage its fly-by-wire flight control system, four computers, without which the airplane could not have maintained controlled flight. To help pilots cope with the airplane’s 9-G capability, the seat reclined 30 degrees, and the side-mounted control stick had a rest to support the pilot’s arm when it weighed many times normal. A “hands-on throttle and stick” put all the vital buttons, switches, and toggles at the pilot’s fingertips, and also eliminated the need for the Guy In Back.

Although the Air Force expected the F-15 to be a good dogfighter, its primary mission—intercept Soviet MiG-25s—required a bulky radar and a load of medium-range Sparrow missiles, which drove up weight and expense. Appalled by the escalating costs of the C-5 Galaxy heavy lifter and the F-111 swing-wing, multi-role fighter, some advocates in the Pentagon, led in the Air Force by “Mad Major” John Boyd, pushed for an inexpensive, lightweight, highly maneuverable platform that would be used only as a daytime fighter.

Retired General Mike Loh, a fighter requirements staff officer at the Pentagon during the early 1970s, became part of Boyd’s “Fighter Mafia,” Air Force officers and civilian defense analysts who advocated air-combat maneuverability over heavy—and heavily armed—fighters. Loh, a fighter pilot, test pilot, and self-described “technical guy,” first met Boyd in 1965 at Florida’s Eglin Air Force Base and became intrigued by his energy maneuverability (EM) theories for comparing fighter performance. In October 1969, after attending the Air Force Test Pilot School and spending a year in Vietnam, Loh requested an assignment to work for Boyd at the Pentagon.

During the day, he worked on modifying existing aircraft. At night, he worked with the team who applied Boyd’s EM concepts to determine the overall weight, wing area, and thrust requirements for a lightweight fighter that could gain the upper hand on another jet by turning and climbing faster in a given situation. Loh spent so much time talking to Boyd on the phone in the evenings that he still remembers Boyd’s phone number. (Boyd died in 1997.)

Loh says that each Fighter Mafia member had a different agenda. “Boyd was unquestionably the leader and dominated the crusade. His motivation was to vindicate his EM theory, and he wasn’t concerned about any mission beyond close-in air-to-air combat. He spent hours debating anyone who challenged his views.”