The F-15 is, in a sense, a child of the MiG-25. When the Foxbat appeared in the late 1960s, its huge wing and blistering speed convinced Western intelligence that the Soviets had built a maneuverable super-fighter — a misreading only corrected after Viktor Belenko defected with one to Japan in 1976. But the fear did its work: it pushed the U.S. Air Force to fund a fighter that could out-fly anything in the sky.

Combined with the hard lessons of Vietnam — where agile MiG-17s and MiG-21s embarrassed heavier American jets — the F-X programme produced an aircraft with an enormous wing, low wing loading and two powerful afterburning turbofans. The result had a thrust-to-weight ratio above one at combat weight, letting the Eagle accelerate vertically. The Foxbat scare had, ironically, produced its own antidote.

Most fighters trade away energy in a hard turn or a steep climb. The F-15 was designed so it did not have to. With a big low-loaded wing generating lift cheaply and two F100s producing more thrust than the jet’s combat weight, the Eagle has surplus power in almost every part of the envelope. It can point its nose at the sky and keep accelerating — the same energy margin that let a stripped “Streak Eagle” shatter eight time-to-climb records in 1975, and that lets a combat Eagle regain lost speed and altitude faster than its opponent.

Air combat since the 1970s has been decided as much by sensors as by turning ability. The APG-63 gave the F-15 a long-range pulse-Doppler picture with genuine look-down/shoot-down performance, so a low-flying target could no longer hide in ground return. Married to the semi-active AIM-7 Sparrow and later the fire-and-forget AIM-120 AMRAAM, that radar let Eagle crews shoot at range and turn away — the pattern behind many of the type’s Gulf War kills, where Iraqi jets were destroyed before they ever detected the Eagle hunting them.

Historic flyaway figures for the F-15A/C cluster around US$30 million apiece (roughly $29.9M is commonly cited), though such numbers vary by variant, year and how you count development. Operating costs are harder still: no single reliable public cost-per-flight-hour figure exists for the A–D Eagle, and quoted numbers depend heavily on the accounting method and the fleet’s age. What is clear is that the F-15 was a deliberately expensive, no-compromise machine — the opposite philosophy to the cheap, mass-built MiG-21 it was meant to defeat. The new-build F-15EX Eagle II carries a far higher modern price tag again.