(CNN) A $12 billion makeover is underway for the US Air Force's 1980's-era F-15 fighter, a step towards upgrading an air fleet that one military official recently called the "smallest, oldest and least ready" in history.
The F-15 has long been hailed as the most successful dog-fighting aircraft in US history, boasting an undefeated air-to-air combat record with more than 100 aerial combat victories, according to Boeing, the plane's primary contractor and developer.

The Air Force initially planned to replace the entire F-15 fleet with the fifth-generation F-22 Raptor, but production of the stealthy aircraft was halted in 2009 and only 188 of the 749 F-22s purchased by the Pentagon were ever produced.

With rival nations like China and Russia quickly closing the technology gap that has allowed the US to rule the skies for decades and fewer F-22s than expected at its disposal, the Air Force has decided to invest in a major facelift for the battle-tested F-15 to help fill the void by extending its lifespan through 2040.

The upgrade will cover 435 F-15s, boosting them with new radar technology, updated mission computer systems, modern communication tools, advanced infrared search and track capabilities and electronic warfare defenses so the F-15s can work in concert with more advanced aircraft, the Air Force told CNN.

Many of the upgraded F-15's will also be modified to carry 16 missiles, rather than the standard eight, giving those aircraft greater lethality, said Boeing spokesman Randy Jackson. ...


...The various upgrades will finish installing between 2024 and 2030, according to the Air Force.